Information on EC 2.4.1.22 - lactose synthase

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The expected taxonomic range for this enzyme is: Eukaryota, Bacteria

EC NUMBER
COMMENTARY hide
2.4.1.22
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RECOMMENDED NAME
GeneOntology No.
lactose synthase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
UDP-alpha-D-galactose + D-glucose = UDP + lactose
show the reaction diagram
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
hexosyl group transfer
-
-
-
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
Galactose metabolism
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-
Metabolic pathways
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-
SYSTEMATIC NAME
IUBMB Comments
UDP-galactose:D-glucose 4-beta-D-galactosyltransferase
The enzyme is a complex of two proteins, A and B. In the absence of the B protein (alpha-lactalbumin), the enzyme catalyses the transfer of galactose from UDP-alpha-D-galactose to N-acetylglucosamine (EC 2.4.1.90 N-acetyllactosamine synthase).
CAS REGISTRY NUMBER
COMMENTARY hide
9030-11-9
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ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
-
-
-
Manually annotated by BRENDA team
alpha-lactalbumin fragment; Northern fur seal
UniProt
Manually annotated by BRENDA team
-
-
-
Manually annotated by BRENDA team
alpha-lactalbumin; Weddell seal
UniProt
Manually annotated by BRENDA team
female
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-
Manually annotated by BRENDA team
alpha-lactalbumin fragment; Australian sea lion
UniProt
Manually annotated by BRENDA team
alpha-lactalbumin; atlantic walrus
UniProt
Manually annotated by BRENDA team
-
-
-
Manually annotated by BRENDA team
alpha-lactalbumin fragment; i.e. Pusa hispida, ringed seal
UniProt
Manually annotated by BRENDA team
alpha-lactalbumin; California sealion
UniProt
Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
malfunction
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
alpha-UDP-D-galactose + D-glucose
UDP + lactose
show the reaction diagram
-
inversion of anomeric configuration to form beta-O-galactosides
-
-
?
alpha-UDP-D-galactose + N-acetyl-D-glucosamine
UDP + alpha-D-galactosyl(1-4)beta-N-acetyl-D-glucosamine
show the reaction diagram
-
-
-
-
?
dUDPgalactose + D-glucose
lactose + dUDP
show the reaction diagram
UDP-D-galactose + D-glucose
UDP + lactose
show the reaction diagram
-
lactose synthesis is achieved only in the presence of alpha-lactalbumin. In absence of alpha-lactalbumin the enzyme catalyzes the reaction of EC 2.4.1.90
-
-
?
UDP-galactose + D-glucose
UDP + lactose
show the reaction diagram
UDP-galactose + N-acetyl-D-glucosamine
UDP + D-galactosyl(1-4)beta-N-acetyl-D-glucosamine
show the reaction diagram
UDP-glucose + N-acetyl-D-glucosamine
UDP + D-glucosyl(1-4)beta-N-acetyl-D-glucosamine
show the reaction diagram
-
about 20% activity compared to UDP-galactose
-
-
?
UDPgalactose + alpha-methyl-D-glucose
?
show the reaction diagram
-
-
-
-
?
UDPgalactose + cellobiose
?
show the reaction diagram
-
7.5% of the activity of glucose
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-
?
UDPgalactose + D-glucose
lactose + UDP
show the reaction diagram
UDPgalactose + D-xylose
?
show the reaction diagram
-
-
-
-
?
UDPgalactose + gentiobiose
?
show the reaction diagram
-
-
-
-
?
UDPgalactose + glucose
lactose + UDP
show the reaction diagram
-
biosynthesis of lactose
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-
?
UDPgalactose + maltose
?
show the reaction diagram
-
-
-
-
?
additional information
?
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
UDP-galactose + D-glucose
UDP + lactose
show the reaction diagram
UDPgalactose + glucose
lactose + UDP
show the reaction diagram
-
biosynthesis of lactose
-
-
?
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Ca2+
-
25% of the activation with Mn2+
Mg2+
-
25% of the activation with Mn2+
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
2,4,6-Trinitrobenzenesulfonate
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modification of alpha-lactalbumin
2-deoxy-D-glucose
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0.4 M, 68% inhibition
2-Hydroxy-5-nitrobenzyl bromide
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modification of alpha-lactalbumin
2-mercaptoethanol
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modification of alpha-lactalbumin
2-Nitrophenylsulfenyl chloride
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modification of alpha-lactalbumin
acetone
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20% v/v, 69% inhibition
acetonitrile
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20% v/v, complete inhibition
alpha-lactalbumin
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inhibits galactosyl transfer to N-acetylglucosamine
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Ca2+
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above 4 mM
carbodiimide
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at pH 4.5 rapid loss of the biological activity of alpha-lactalbumin
D-arabinose
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0.4 M, 13% inhibition
D-ribose
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0.4 M, 59% inhibition
D-xylose
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0.4 M, 36% inhibition
Dimethyl-(2-hydroxy-5-nitrobenzyl)-sulfonium bromide
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modification of alpha-lactalbumin
Dimethylsulfoxide
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20% v/v, 43% inhibition
dioxane
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20% v/v, 88% inhibition
dithiothreitol
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the rate of reduction of the disulfide bond in alpha-lactalbumin is much faster with dithiothreitol than mercaptoethanol, and at 24°C proceeds to completion within minutes at pH 8
ethanol
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20% v/v, 4% inhibition
Formylkynurenine
glycinamide
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at pH 4.5 rapid loss of the biological activity of alpha-lactalbumin
Iodine
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iodoacetate
L-arabinose
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0.4 M, 54% inhibition
L-sorbose
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0.4 M, 45% inhibition
L-Xylose
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0.4 M, 16% inhibition
Maleic anhydride
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-
Mg2+
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above 4 mM
N,N-Dimethylformamide
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20% v/v, 90% inhibition
N-Acetylimidazole
N-methylpyrrolidone
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20% v/v, complete inhibition
tetrahydrofuran
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20% v/v, complete inhibition
Tetranitromethane
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tunicamycin
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UDPglucose
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vincristine
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additional information
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alpha-lactalbumin strongly inhibits the transfer of galactose to free N-acetylglucosamine
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
alpha-lactalbumin
methanol
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20% v/v, 17% activation
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
1.7 - 1400
glucose
0.009 - 0.06
UDPgalactose
additional information
additional information
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
additional information
additional information
Bos taurus
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-
-
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
TEMPERATURE RANGE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
20 - 37
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
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trans-Golgi complex, beta1,4-galactosyltransferase-I
Manually annotated by BRENDA team
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alpha-lactalbumin in synthesized on the rough endoplasmic reticulum
Manually annotated by BRENDA team
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
50000
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recombinant enzyme, gel filtration
60000
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complex between galactosyl transferase and alpha-lactalbumin, equilibrium sedimentation
75000
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gel filtration
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
?
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x * 50000, recombinant enzyme, SDS-PAGE
dimer
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1 * 14500, alpha-lactalbumin, + 1 * 46000, galactosyl transferase, equilibrium sedimentation
additional information
POSTTRANSLATIONAL MODIFICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
glycoprotein
Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
catalytic domain of recombinant bovine beta4Gal-T1 from residues 130 to 402, d129 beta4Gal-T1, 33000 Da, and mouse recombinant alpha-lactalbumin. Crystal structure of enzyme bound with various substrates
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wild-type and mutant enzyme in closed conformation induced by UDP-galactose, X-ray diffraction structure determination and analysis at 2.3 A resolution, re-refinement or previously determined crystal structures of enzyme complexed with different substrates and Mn2+, overview
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catalytic domain of recombinant bovine beta4Gal-T1 from residues 130 to 402, d129 beta4Gal-T1, 33000 Da, and mouse recombinant alpha-lactalbumin. Crystal structure of enzyme bound with various substrates
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
galactosyl transferase component
recombinant enzyme fro Escherichia coli
recombinant enzyme from Escherichia coli strain BL21(DE3)
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
DNA and amino acid sequence determination and analysis of alpha-lactalbumin component of the lactose synthase complex, aberrant splicing is responsible for the two cDNA variants isolated from mammary tissue, with the longer variant maintaining the third intron and the shorter variant, phylogenetic analysis; DNA and amino acid sequence determination and analysis of alpha-lactalbumin component of the lactose synthase complex, aberrant splicing is responsible for the two cDNA variants isolated from mammary tissue, with the longer variant maintaining the third intron and the shorter variant, phylogenetic analysis
DNA and amino acid sequence determination and analysis of alpha-lactalbumin component of the lactose synthase complex, phylogenetic analysis
expressed in Escherichia Lec8 Chinese hamster ovary cells
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expression in Escherichia coli
gene B4GALT1, DNA and amino acid sequence determination and analysis, RT-PCR expression analysis, sequence comparison
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
C342T
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determination and analysis of the closed conformation crystal structure of enzyme mutant in complex with UDP-galactose