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Enzyme Nomenclature
Information on EC 2.7.1.6 - galactokinase
for references in articles please use BRENDA:EC2.7.1.6
Word Map on EC 2.7.1.6
- 2.7.1.6
- galactose-1-phosphate
- galactosemia
- cataract
-
leloir
- uridyltransferase
- lambda
-
gale
- thymidine
- udp-galactose
-
uridyl
- bacteriophage
- lactis
- 1-phosphate
- galactitol
- udp-glucose
-
epimerase
-
inborn
- kluyveromyces
-
prophage
-
rho-dependent
-
coliphage
-
presenile
-
gal-1-p
-
antitermination
- phosphomevalonate
-
galactose-induced
- glucose-1-phosphate
-
readthrough
- udp-galactose-4-epimerase
-
4'-epimerase
-
counterselection
- synthesis
- nutrition
- medicine
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Specify your search results
The expected taxonomic range for this enzyme is: Eukaryota, Bacteria, Archaea
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EC NUMBER 
COMMENTARY 
2.7.1.6
-
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RECOMMENDED NAME
GeneOntology No.
galactokinase
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
ATP + alpha-D-galactose = ADP + alpha-D-galactose 1-phosphate
the most likely kinetic mechanism is an ordered ternary complex in which ATP is the first substrate to bind
-
ATP + alpha-D-galactose = ADP + alpha-D-galactose 1-phosphate
mechanism of D-galactose and nucleotide binding
-
ATP + alpha-D-galactose = ADP + alpha-D-galactose 1-phosphate
mechanism of the reaction is sequential in both directions. Residue Asp183 acts as a catalytic base that deprotonates the C1 hydroxyl group of galactose. The pH-kcat profile of the synthesis of galactose 1-phosphate has a pKa of 6.9 likely due to Asp183. The pH-kcat/KGal profile of the reverse reaction lacks a key pKa required for a direct proton transfer mechanism. Arg36 may lower the pKa of the C1 hydroxyl to facilitate deprotonation
-
ATP + alpha-D-galactose = ADP + alpha-D-galactose 1-phosphate
-
-
-
-
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
phospho group transfer
-
-
-
-
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
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SYSTEMATIC NAME
IUBMB Comments
ATP:D-galactose 1-phosphotransferase
Part of the Leloir pathway for galactose metabolism. The enzymes from mammals and from the bacterium Escherichia coli have no activity with N-acetyl-alpha-D-galactosamine [4-6].
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CAS REGISTRY NUMBER
COMMENTARY
9030-53-9
-
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
Japanese patients with GALK deficiency, Caucasian patients with GALK deficiency and Japanese wild-type controls
-
-
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
malfunction
-
an AtGALK T-DNA insertion mutant (atgalk) that (a) is AtGALK transcript deficient, (b) displays no GALK activity in vegetative tissues; and (c) accumulates Gal up to 6.8 mg/g FW in vegetative tissues, in contrast to wild-type plants. By constitutively overexpressing functional AtGALK cDNA, atgalk is functionally rescued
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
2'-dATP + D-galactose
2'-dADP + alpha-D-galactose 1-phosphate
-
-
-
-
?
2-amino-2-deoxy-D-galactose + ATP
2-amino-2-deoxy-D-galactose 1-phosphate + ADP
-
-
-
-
?
3'-dATP + D-galactose
3'-dADP + alpha-D-galactose 1-phosphate
-
-
-
-
?
ATP + 2-amino-2-deoxy-D-galactose
ADP + 2-amino-2-deoxy-D-galactose 1-phosphate
-
-
-
-
?
ATP + 3-deoxy-3-methyl-D-galactose
ADP + 3-deoxy-3-methyl-D-galactose 1-phosphate
-
-
-
-
?
ATP + 4-deoxy-D-galactose
ADP + 4-deoxy-alpha-D-galactose 1-phosphate
-
substrate only for mutants Y223F, Y223W
-
-
?
ATP + 6-deoxy-D-galactose
ADP + 2-amino-2-deoxy-D-galactose 1-phosphate
-
-
-
-
?
ATP + D-galactosamine
ADP + alpha-D-galactosamine 1-phosphate
-
substrate: D-galactosamine, specific activity: 12.5 micromol/min/mg
-
-
?
ATP + D-galacturonic acid
ADP + alpha-D-galacturonic acid 1-phosphate
-
substrate: galacturonic acid, specific activity: 0.09 micromol/min/mg
-
-
?
ATP + D-talose
ADP + alpha-D-talose 1-phosphate
-
substrate only for mutants Y223F, Y223W
-
-
?
ATP + L-glucose
ADP + alpha-L-glucose 1-phosphate
-
substrate only for mutants Y223F, Y223W
-
-
?
ATP + N-acetyl-D-galactosamine
ADP + N-acetyl-alpha-D-galactosamine 1-phosphate
-
-
-
-
?
CTP + D-galactose
CDP + alpha-D-galactose 1-phosphate
-
substrate: CTP, specific activity: 0.551 micromol/min/mg
-
-
?
dATP + D-galactose
dADP + alpha-D-galactose 1-phosphate
-
substrate: dATP, specific activity: 138 micromol/min/mg
-
-
?
dCTP + D-galactose
dCDP + alpha-D-galactose 1-phosphate
-
substrate: dCTP, specific activity: 0.931 micromol/min/mg
-
-
?
dGTP + D-galactose
dGDP + alpha-D-galactose 1-phosphate
-
substrate: dGTP, specific activity: 31.9 micromol/min/mg
-
-
?
dTTP + D-galactose
?
-
substrate: dTTP, specific activity: 2.5 micromol/min/mg
-
-
?
dUTP + D-galactose
dUDP + alpha-D-galactose 1-phosphate
-
substrate: dUTP, specific activity: 1.5 micromol/min/mg
-
-
?
GTP + D-galactose
GDP + alpha-D-galactose 1-phosphate
-
substrate: GTP, specific activity: 28.5 micromol/min/mg
-
-
?
ITP + D-galactose
IDP + alpha-D-galactose 1-phosphate
-
substrate: ITP, specific activity: 15.7 micromol/min/mg
-
-
?
UTP + D-galactose
UDP + alpha-D-galactose 1-phosphate
-
substrate: UTP, specific activity: 0.52 micromol/min/mg
-
-
?
ATP + 2-deoxy-D-galactose
ADP + 2-deoxy-alpha-D-galactose 1-phosphate
-
substrate: 2-deoxygalactose, specific activity: 99.7 micromol/min/mg
-
-
?
ATP + 2-deoxy-D-galactose
ADP + 2-deoxy-alpha-D-galactose 1-phosphate
-
-
-
-
?
ATP + 2-deoxy-D-galactose
ADP + 2-deoxy-alpha-D-galactose 1-phosphate
-
-
-
-
?
ATP + 2-deoxy-D-galactose
ADP + 2-deoxy-alpha-D-galactose 1-phosphate
-
-
-
-
?
ATP + 2-deoxy-D-galactose
ADP + 2-deoxy-D-galactose 1-phosphate
-
-
-
-
?
ATP + 6-deoxy-D-galactose
ADP + 6-deoxy-alpha-D-galactose 1-phosphate
-
substrate: 6-deoxygalactose, specific activity: 0.0781 micromol/min/mg
-
-
?
ATP + 6-deoxy-D-galactose
ADP + 6-deoxy-alpha-D-galactose 1-phosphate
-
-
-
-
?
ATP + D-galactose
ADP + alpha-D-galactose 1-phosphate
-
very strict substrate specificity for galactose and ATP
-
-
-
ATP + D-galactose
ADP + alpha-D-galactose 1-phosphate
-
substrate: ATP, specific activity: 137 micromol/min/mg
-
-
?
ATP + D-galactose
ADP + alpha-D-galactose 1-phosphate
-
substrate: D-galactose, specific activity: 158 micromol/min/mg
-
-
?
ATP + D-galactose
ADP + alpha-D-galactose 1-phosphate
-
-
-
-
?
ATP + D-galactose
ADP + alpha-D-galactose 1-phosphate
-
-
-
-
-
ATP + D-galactose
ADP + alpha-D-galactose 1-phosphate
-
unidirectional towards galactose phosphorylation
-
-
ir
ATP + D-galactose
ADP + alpha-D-galactose 1-phosphate
-
-
-
-
?
ATP + D-galactose
ADP + alpha-D-galactose 1-phosphate
-
-
-
-
?
ATP + D-galactose
ADP + alpha-D-galactose 1-phosphate
-
-
-
?
ATP + D-galactose
ADP + alpha-D-galactose 1-phosphate
-
-
-
-
?
ATP + galactose
ADP + alpha-D-galactose 1-phosphate
-
the enzyme catalyzes the first step in the conversion of galactose to glucose. Galactokinase deficiency is characterized by galactosemia, galactosuria and cataract formation in early childhood
-
-
?
ATP + galactose
ADP + alpha-D-galactose 1-phosphate
-
galactokinase deficiency is an autosomal recessive disorder, which causes cataract formation in children not maintained on a lactose-free diet
-
-
?
ATP + galactose
ADP + alpha-D-galactose 1-phosphate
-
galaktokinase deficiency is an autosomal recessive disorder characterized by hypergalactosemia and cataract formation
-
-
?
ATP + galactose
ADP + alpha-D-galactose 1-phosphate
-
lack of fully functional galactokinase is one cause of the inherited disease galactosemia, the main clinical manifestation of which is the early onset of cataracts
-
-
?
ATP + galactose
ADP + alpha-D-galactose 1-phosphate
-
first step in the Leloir pathway for galactose metabolism
-
-
?
additional information
?
-
-
no tolerance for C-4 changes in the substrate
-
-
-
additional information
?
-
-
no substrate: N-acetyl-D-galactosamine, L-arabinose, D-fucose, D-glucose
-
-
-
additional information
?
-
-
amino acid side chains responsible for anchoring the sugar ligand to the protein include Arg36, Glu42, Asp45, ASp183, and Tyr233
-
-
-
additional information
?
-
-
mechanism of the reaction is sequential in both directions. Residue Asp183 acts as a catalytic base that deprotonates the C1 hydroxyl group of galactose. The pH-kcat profile of the synthesis of galactose 1-phosphate has a pKa of 6.9 likely due to Asp183. The pH-kcat/KGal profile of the reverse reaction lacks a key pKa required for a direct proton transfer mechanism. Arg36 may lower the pKa of the C1 hydroxyl to facilitate deprotonation
-
-
-
additional information
?
-
-
galactokinase Gal1p is a regulator of transcription. Gal1p activates Gal4p, the activator of GAL genes. Gal1p activates Gal4p by direct interaction with the Gal4p inhibitor Gal80p. Interaction requires galactose, adenosine triphosphate and the regulatory function of Gal1p. The gal1p-gal80p complex formation results in the inactivation of Gal80p, thereby transmitting the galactose signal to Gal4p
-
-
-
additional information
?
-
-
L-arabinose, D-fucose, L-glucose, and D-talose are no substrates
-
-
-
additional information
?
-
-
L-arabinose, D-fucose, L-glucose, and D-talose are no substrates
-
-
-
additional information
?
-
-
key enzyme for cellulase induction during growth on lactose
-
-
-
additional information
?
-
-
induction of the gal pathway and cellulase genes involves no transcriptional inducer function of the galactokinase in Hypocrea jecorina
-
-
-
additional information
?
-
-
induction of the gal pathway and cellulase genes involves no transcriptional inducer function of the galactokinase in Hypocrea jecorina
-
-
-
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
ATP + galactose
ADP + alpha-D-galactose 1-phosphate
-
the enzyme catalyzes the first step in the conversion of galactose to glucose. Galactokinase deficiency is characterized by galactosemia, galactosuria and cataract formation in early childhood
-
-
?
ATP + galactose
ADP + alpha-D-galactose 1-phosphate
-
galactokinase deficiency is an autosomal recessive disorder, which causes cataract formation in children not maintained on a lactose-free diet
-
-
?
ATP + galactose
ADP + alpha-D-galactose 1-phosphate
-
galaktokinase deficiency is an autosomal recessive disorder characterized by hypergalactosemia and cataract formation
-
-
?
ATP + galactose
ADP + alpha-D-galactose 1-phosphate
-
lack of fully functional galactokinase is one cause of the inherited disease galactosemia, the main clinical manifestation of which is the early onset of cataracts
-
-
?
ATP + galactose
ADP + alpha-D-galactose 1-phosphate
-
first step in the Leloir pathway for galactose metabolism
-
-
?
additional information
?
-
-
galactokinase Gal1p is a regulator of transcription. Gal1p activates Gal4p, the activator of GAL genes. Gal1p activates Gal4p by direct interaction with the Gal4p inhibitor Gal80p. Interaction requires galactose, adenosine triphosphate and the regulatory function of Gal1p. The gal1p-gal80p complex formation results in the inactivation of Gal80p, thereby transmitting the galactose signal to Gal4p
-
-
-
additional information
?
-
-
key enzyme for cellulase induction during growth on lactose
-
-
-
additional information
?
-
-
induction of the gal pathway and cellulase genes involves no transcriptional inducer function of the galactokinase in Hypocrea jecorina
-
-
-
additional information
?
-
-
induction of the gal pathway and cellulase genes involves no transcriptional inducer function of the galactokinase in Hypocrea jecorina
-
-
-
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Ca2+
Co2+
Fe2+
Mg2+
Mn2+
additional information
Ca2+
-
absolute requirement for a divalent cation, Ca2+ can be partially replaced by Co2+
Ca2+
-
divalent cations activity in the order of decreasing efficiency: Mn2+, Mg2+, Ca2+, Fe2+
Co2+
-
absolute requirement for a divalent cation, Mg2+ can be partially replaced by Co2+
Co2+
-
divalent cations activate in the order of decreasing efficiency: Mn2+, Mg2+, Ca2+, Fe2+
Co2+
-
divalent cation required, in the order of decreasing efficiency: Mg2+, Co2+, Mn2+, Fe2+
Fe2+
-
divalent cations activity in the order of decreasing efficiency: Mn2+, Mg2+, Ca2+, Fe2+
Fe2+
-
divalent cation required, in the order of decreasing efficiency: Mg2+, Co2+, Mn2+, Fe2+
Mg2+
-
absolute requirement for a divalent cation, maximally active in presence of 5 mM Mg2+
Mg2+
-
divalent cations activate in the order of decreasing efficiency: Mn2+, Mg2+, Ca2+, Fe2+
Mg2+
-
divalent cation required, in the order of decreasing efficiency: Mg2+, Co2+, Mn2+, Fe2+
Mg2+
most effective divalent cation; most effective divalent cation
Mn2+
-
can partly substitute Mg2+, with the reduction of the activity by about 21%
Mn2+
-
absolute requirement for a divalent cation, Mg2+ can be partially replaced by Co2+
Mn2+
-
divalent cations activate in the order of decreasing efficiency: Mn2+, Mg2+, Ca2+, Fe2+
Mn2+
-
divalent cation required, in the order of decreasing efficiency: Mg2+, Co2+, Mn2+, Fe2+
Mn2+
62% of the activity with Mg2+; 62% of the activity with Mg2+
additional information
divalent cation required; divalent cation required
additional information
divalent cation required; divalent cation required
additional information
-
divalent cation required; divalent cation required
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INHIBITORS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
2-(1,3-benzoxazol-2-ylamino)-4-(4-chloro-1H-pyrazol-3-yl)-4,6,7,8-tetrahydroquinazolin-5(1H)-one
-
inhibitory to isoform Galk1, no inhibition of isoform Galk2 up to 40 microM. Uncompetitive with respect to galactose, compound directly competes with ATP at the binding site, and galactose may be required to bind first. Compound is able to lower galactose 1-phosphate levels in primary fibroblasts of patients suffering Classic Galactosemia without significant effect on viability of cells
NaCl
50500 mM, the enzymatic activity decreases approximately 40%60%, respectively; 50500 mM, the enzymatic activity decreases approximately 40%60%, respectively
ADP
-
competitive with respect to ATP, uncompetitive with respect to galactose
alpha-D-galactose 1-phosphate
-
uncompetitive inhibitor with respect to galactose, mixed inhibitor with respect to ATP
Hg2+
-
0.5 mM HgCl2, complete inhibition, activity is completely restored by 1 mM dithiothreitol
PCMB
-
0.1 mM, complete inhibition, activity is completely restored by 1 mM dithiothreitol
additional information
-
not inhibitory: N-acetyl-D-galactosamine, L-arabinose, D-fucose, D-glucose
-
additional information
-
Hg-containing compounds at 0.4 mM completely block the enzyme
-
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
KCl
50-100 mM, about 80% increase in activity; 50-100 mM, about 80% increase in activity
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.046
ATP
-
in the presence of 2-deoxy-D-galactose as a substrate, at 30°C, wild type enzyme
0.057
ATP
-
in the presence of D-galactose as a substrate, wild type enzyme
0.225
ATP
-
in the presence of D-glucose as a substrate, at 30°C, wild type enzyme
0.36
ATP
pH 8.6, temperature not specified in the publication
0.091
D-galactose
pH 8.6, temperature not specified in the publication
0.108
D-galactose
pH 8.6, temperature not specified in the publication
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TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.38
D-galactose
pH 8.6, temperature not specified in the publication
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kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
3.5
D-galactose
pH 8.6, temperature not specified in the publication
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Ki VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.41
ATP
isoform GalK2, pH 8.6, temperature not specified in the publication
28
alpha-D-galactose 1-phosphate
-
pH 8, 37°C, uncompetitive inhibition constant with respect to galactose
39
alpha-D-galactose 1-phosphate
-
pH 8, 37°C, uncompetitive inhibition constant with respect to ATP
90
alpha-D-galactose 1-phosphate
-
pH 8, 37°C, competitive inhibition constant with respect to ATP
3.5
D-galactose 1-phosphate
-
pH 7.3, 25°C, competitive inhibition with galactose as the variable substrate
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IC50 VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.0047
2-(1,3-benzoxazol-2-ylamino)-4-(4-chloro-1H-pyrazol-3-yl)-4,6,7,8-tetrahydroquinazolin-5(1H)-one
Homo sapiens
-
isoform Galk1, pH not specified in the publication, temperature not specified in the publication
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
0.0781
-
substrate: ATP + 6-deoxy-D-galactose, pH 8, 37°C
0.09
-
substrate: ATP + D-galacturonic acid, pH 8, 37°C
99.7
-
substrate: ATP + 2-deoxy-D-galactose, pH 8, 37°C
additional information
additional information
1.04 units/mg for strain IMDOST40 and 0.41 units/mg for strain IMDOST07 in 100 mM triethanolamine buffer (pH 7.8), containing 5 mM MgCl2, 2 mM phosphoenolpyruvate, 2 mM ATP, and 10 mM galactose
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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pH RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
5.5 - 8
-
pH 5.5: about 60% of maximal activity, pH 8.0: about 70% of maximal activity, potassium phosphate buffer
6.7 - 8.7
-
pH 6.7: about 45% of maximal activity, pH 8.7: about 35% of maximal activity
7 - 9
7 - 9
-
pH-optimum at pH 8 with a sharp drop in activity above pH 9.0 and a more gradual drop below pH 7.0
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TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
45
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TEMPERATURE RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
20 - 60
-
20°C: about 30% of maximal activity, 60°C: about 40% of maximal activity
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pI VALUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
5.7
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SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SOURCE
expression of both isoforms GalK1 and GalK2; expression of both isoforms GalK1 and GalK2
expression of both isoforms GalK1 and GalK2; expression of both isoforms GalK1 and GalK2
-
activity is high at birth and decrases so that by the age of approximately 4 years it reaches the adult value
-
of 2-week-old piglets. Activities in livers of fetal or suckling mammals and decreases at weaning so that the activity in adults is between 10 and 20% of the maximum attained during development
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LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
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PDB
SCOP
CATH
ORGANISM
UNIPROT
Lactococcus lactis subsp. lactis (strain IL1403)
Pyrococcus furiosus (strain ATCC 43587 / DSM 3638 / JCM 8422 / Vc1)
Pyrococcus horikoshii (strain ATCC 700860 / DSM 12428 / JCM 9974 / NBRC 100139 / OT-3)
Pyrococcus horikoshii (strain ATCC 700860 / DSM 12428 / JCM 9974 / NBRC 100139 / OT-3)
Pyrococcus horikoshii (strain ATCC 700860 / DSM 12428 / JCM 9974 / NBRC 100139 / OT-3)
Saccharomyces cerevisiae (strain ATCC 204508 / S288c)
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MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
46000
-
gel filtration, calculation from sedimentation and diffusion data
50000
gel filtration, both isoforms GalK1 and GalK2; gel filtration, both isoforms GalK1 and GalK2
58000
60000
additional information
58000
-
equilibrium sedimentation, sucrose density gradient centrifugation
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SUBUNITS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
dimer
monomer
monomer
1 * 51300, calculated, 1 * 50000, SDS-PAGE; 1 * 51900, calculated, 1 * 50000, SDS-PAGE
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Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
hanging drop method of vapor diffusion, wild-type and selenomethionine-labeled galactokinase
-
hanging-drop method of vapour diffusion with ammonium sulfate as the precipitant. The crystals diffract X-rays to 2.9 A resolution on a synchroton-radiation source
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in complex with MgADP and D-galactose, comparison with S. cerevisiae enzymes
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seeding method in combination with the sitting-drop vapour-diffusion method using 30%(v/v) PEG 400, 1 M D-galactose, 5 mM AMP-PNP, 5% (w/v) PEG 4000, 50 mM MgCl2 and 0.1 M MES pH 6.3.
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hanging drop vapour diffusion method using 18-25% poly(ethylene glycol) 8000 containing 200 mM LiCl buffered with 100 mM MES3 (pH 6.0) and enzyme concentrations of 15.0 mg/ml and 5 mM Mg-adenosine 5'-(beta, gamma-imido)triphosphate
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pH STABILITY
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
20 - 45
-
pH 7.3, 50 mM phosphate buffer, 10 mM 2-mercaptoethanol, 5% glycerol, 60 min, stable
50
60
90
90
-
10 min, in presence of 2 mM dithiothreitol or dithioerythritol, 50% loss of activity
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GENERAL STABILITY
ORGANISM
UNIPROT
LITERATURE
dithiothreitol protects the enzyme better than 2-mercaptoethanol against denaturation on storage at 4°C
-
overnight dialysis at pH above 9.2 or below pH 5.5 results in loss of all enzymatic activity
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the enzyme is stabilized during the purification procedure by the inclusion of 10% glycerol, 1 mM phosphate and 20 mM 2-mercaptoethanol in all buffer solutions
-
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STORAGE STABILITY
ORGANISM
UNIPROT
LITERATURE
-20°C, unstable in 0.01 M KH2PO4-K2HPO4, pH 7.2 buffer, 0.01 M MgCl2, 1 mM dithiothreitol, 0.2 mM ATP without glycerol
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0°C, galactokinase suspension in saturated (NH4)2SO4 retains at least 80% of its activity after 1 week
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4°C, 0.01 M KH2PO4-K2HPO4, pH 7.2 buffer, 0.01 M MgCl2, 1 mM dithiothreitol, about 40% loss of activity after 24 h
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4°C, potassium phosphate buffer, pH 7.5, more than 80% of the initial activity remains after 1 week
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
HiTrap Q column chromatography, HiTrap Phenyl FF column chromatography, and HiLoad 16/60 Superdex 75 gel filtration
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nickel-nitrilotriacetic acid-agarose chromatography and Resource-Q column chromatography
-
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
expressed in Escherichia coli
expression in COS cells, galactokinase maps to the distal region of mouse chromosome 11
-
expression in Escherichia coli
expression in Escherichia coli; expression in Escherichia coli
gene from Escherichia coli K-12 is subcloned into pET-15b vector and overexpressed in BL21 cells
-
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
enhanced gene expression caused by a nucleotide variation within GALKI promoter (c.-22T>C mutation)
-
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
M173L
-
moderate activity on D-glucose, wider substrate specificity than wild-type
M173L/Y371H
-
acts on additional substrates such as 4-azido-4-deoxy-D-galactose, 6-ido-6-deoxy-D-galactose, 6-chloro-6-deoxy-D-galactose, 6-bromo-6-deoxy-D-galactose, 4-deoxy-D-galactose, 6-thio-6-deoxy-D-galactose, 6-thio-6-deoxy-D-glucose, 6-azido-6-deoxy-D-glucose
Y223F
-
activity similar to wild-type, converts additional substrates L-glucose, D-talose, 4-deoxy-D-galactose, less active on D-galactosamine than wild-type
Y223W
-
significant reduction in activity, converts additional substrates L-glucose, D-talose, 4-deoxy-D-galactose, with less efficiency than mutant Y223F, less active on D-galactosamine than wild-type
A198V
A384P
-
mutant enzyme is not present in the soluble fraction after sonication and can not be purified
C32M
-
mutant enzyme is not present in the soluble fraction after sonication and can not be purified
G346S
-
mutant enzyme shows substantial reduction in turnover number. Lower specificity constant for galactose than wild-type enzyme
G347S
-
mutant enzyme shows substantial reduction in turnover number, increase in Km-value for galactose. Lower specificity constant for galactose than wild-type enzyme
G349S
G36R
-
mutant enzyme is not present in the soluble fraction after sonication and can not be purified
H44Y
-
increrase in Km-value for galactose compared to wild-type. Lower specificity constant for galactose than wild-type enzyme
P28T
-
mutant enzyme is not present in the soluble fraction after sonication and can not be purified
R256W
-
drastic reduction of activity when expressed in COS cells, missense mutation causes GALK deficiency
T288M
-
mutant enzyme is not present in the soluble fraction after sonication and can not be purified
T344M
-
drastic reduction of activity when expressed in COS cells, missense mutation causes GALK deficiency
D186A
-
residue D186 interacts with galactose, possible catalytic residue, no activity of mutant enzyme
D186E
-
residue D186 interacts with galactose, possible catalytic residue, no activity of mutant enzyme
D186N
-
residue D186 interacts with galactose, possible catalytic residue, no activity of mutant enzyme
D62A
-
abolishes all detectable galactokinase activity but retains the ability to use D-glucose as a substrate
D62F
-
abolishes all detectable galactokinase activity but retains the ability to use D-glucose as a substrate
D62H
-
abolishes all detectable galactokinase activity but retains the ability to use D-glucose as a substrate
D62L
-
abolishes all detectable galactokinase activity but retains the ability to use D-glucose as a substrate
D62A
-
abolishes all detectable galactokinase activity but retains the ability to use D-glucose as a substrate
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additional information
A198V
-
GALK variant associated with an A198V mutation in three infants with mild GALK deficiency. Km-values from healthy and mutant individuals are similar. The variant A198V probably originates in Japanese and Korean ancestors and is one of the genetic factors that cause cataract in elderly individuals
G349S
-
drastic reduction of activity when expressed in COS cells, missense mutation causes GALK deficiency
G349S
-
lower specificity constant for galactose than wild-type enzyme. Lower specificity constant for galactose than wild-type enzyme
additional information
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all exchanges for D37 are detrimental to the enzyme
additional information
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the two deletions, of 410delG and 509-510delGT , occur at the nucleotide repeats GGGGGG and GTGTGT, respectively and result in in-frame nonsense codons at amino acids 163 and 201. These mutations arise by slipped strand mispairing
additional information
-
enzyme deletion mutant, strain shows reduced growth on D-galactose but is only slightly affected in growth on lactose. In mutant strain, induction of D-galactose-1-phosphate uridylyltransferase by D-galactose, but not by L-arabinose, is impaired
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APPLICATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
medicine
nutrition
-
expression of enzyme in Streptococcus thermophilus, recombinant strain grows on galactose with a generation time of 55 min, which is almost double the generation time on lactose. During growth on milk and under conditions simulating those used to produce mozzarella cheese, recombinant strain grows and produces acid more rapidly than wild-type strain
synthesis
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enzyme mutant Y371H/M173L, substrate range is much wider than wild-type, generation of unnatural sugar 1-phosphates
medicine
-
analysis of residues involved in type II galactosemia within three-dimensional architecture of enzyme
medicine
identification of five mutations of GALK1 gene in five unrelated Korean patients with GALK deficiency and investigaion of their biochemical characteristics using mammalian cell expression studies. Four missense mutations (p.G137R, p.R256W, p.R277Q, and p.V281M) and one small insertion (c.850_851insG) are identified. Among four patients with severely reduced GALK activity, two are found to be homozygotes for p.R256W and the other two are compound heterozygotes for different molecular defects (p.G137R/p.R277Q and p.V281M/c.850_851insG). One patient with moderately decreased GALK activity is heterozygous for p.R256W. Expression analysis in Cos7 cells confirms that each of the mutations results in reduction of GALK activity and causes GALK deficiency
medicine
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in primary fibroblasts of patients suffering Classic Galactosemia, inhibitor 2-(1,3-benzoxazol-2-ylamino)-4-(4-chloro-1H-pyrazol-3-yl)-4,6,7,8-tetrahydroquinazolin-5(1H)-one is able to lower galactose 1-phosphate levels without significant effect on viability of cells
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