Information on EC 4.4.1.2 - homocysteine desulfhydrase

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

EC NUMBER
COMMENTARY hide
4.4.1.2
-
RECOMMENDED NAME
GeneOntology No.
homocysteine desulfhydrase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
2-aminobut-2-enoate = 2-iminobutanoate
show the reaction diagram
spontaneous
-
-
-
2-iminobutanoate + H2O = 2-oxobutanoate + NH3
show the reaction diagram
spontaneous
-
-
-
L-homocysteine + H2O = hydrogen sulfide + NH3 + 2-oxobutanoate
show the reaction diagram
overall reaction
-
-
-
L-homocysteine = hydrogen sulfide + 2-aminobut-2-enoate
show the reaction diagram
(1a)
-
-
-
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
elimination
-
-
of H2S or RSH, C-S bond cleavage
-
PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
Sulfur metabolism
-
-
SYSTEMATIC NAME
IUBMB Comments
L-homocysteine hydrogen-sulfide-lyase (deaminating; 2-oxobutanoate-forming)
A pyridoxal-phosphate protein. The enzyme cleaves a carbon-sulfur bond, releasing hydrogen sulfide and an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form 2-oxobutanoate and ammonia. The latter reaction, which can occur spontaneously, can also be catalysed by EC 3.5.99.10, 2-iminobutanoate/2-iminopropanoate deaminase
CAS REGISTRY NUMBER
COMMENTARY hide
9024-41-3
-
ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
-
-
-
Manually annotated by BRENDA team
no activity in Crithidia fasciculata
-
-
-
Manually annotated by BRENDA team
no activity in Entamoeba histolytica
-
-
-
Manually annotated by BRENDA team
no activity in Escherichia coli
-
-
-
Manually annotated by BRENDA team
no activity in Herpetomonas muscarum
-
-
-
Manually annotated by BRENDA team
no activity in Leishmania mexicana mexicana
amastigotes and promastigotes
-
-
Manually annotated by BRENDA team
no activity in Leishmania tarentolae
-
-
-
Manually annotated by BRENDA team
no activity in mouse
liver
-
-
Manually annotated by BRENDA team
no activity in Tetrahymena pyriformis
-
-
-
Manually annotated by BRENDA team
no activity in Trichomitus batrachorum
-
-
-
Manually annotated by BRENDA team
no activity in Trichomonas foetus
-
-
-
Manually annotated by BRENDA team
Trichomonas batrachorum
weak
-
-
Manually annotated by BRENDA team
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
glycine + H2O
?
show the reaction diagram
L-alanine + H2O
?
show the reaction diagram
L-asparagine + H2O
?
show the reaction diagram
L-cysteine + H2O
2-oxopropanoate + NH3 + ?
show the reaction diagram
-
43.3% of the oxo-acid release activity compared to L-homocysteine as substrate
-
-
?
L-cystine + H2O
?
show the reaction diagram
L-homocysteine + H2O
H2S + NH3 + 2-oxobutanoate
show the reaction diagram
L-homocysteine + H2O
hydrogen sulfide + NH3 + 2-oxobutanoate
show the reaction diagram
L-lysine + H2O
?
show the reaction diagram
-
27.1% of the oxo-acid release activity compared to L-homocysteine as substrate
-
-
?
L-methionine + H2O
2-oxobutanoate + NH3 + ?
show the reaction diagram
-
90% of the oxo-acid release compared to L-homocysteine as substrate
-
-
?
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
L-homocysteine + H2O
hydrogen sulfide + NH3 + 2-oxobutanoate
show the reaction diagram
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
2,2'-dithiodiethylanol
-
-
2,4-Dichlorophenol
-
-
Dichlorophene
-
-
dithiothreitol
-
10 mM, 86% loss of activity
DL-Penicillamine
-
-
DL-propargylglycine
-
-
Hexachlorophene
-
-
Hg2+
-
10 mM, 95% loss of activity
hydroxylamine
KCl
-
10 mM, 11% loss of activity
L-Cycloserine
-
-
SDS
-
10 mM, 78% loss of activity
Tween 80
-
1 mM, about 40% loss of activity
additional information
-
no inhibition by EDTA
-
ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
pyridoxal 5'-phosphate
-
-
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.549
homocysteine
-
-
4.9
L-cysteine
-
pH 7.0, 35C
2.46
L-homocysteine
-
pH 7.0, 35C
4.1
L-methionine
-
pH 7.0, 35C
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.00077
L-cysteine
Aspergillus fumigatus
-
pH 7.0, 35C
0.00139
L-homocysteine
Aspergillus fumigatus
-
pH 7.0, 35C
0.00097
L-methionine
Aspergillus fumigatus
-
pH 7.0, 35C
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
8.48
-
pH 7.0, 35C, solid state fermentation, purified enzyme
16.6
-
pH 7.0, 35C, submerged fermentation, purified enzyme
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
pI VALUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
5
-
isoelectric focusing, detected by pH precipitation with no glycosyl residues
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
50000
-
x * 50000, SDS-PAGE
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
pH STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
3
-
4C, 2 h, 50% reduction in enzyme activity
722937
6.5 - 7.8
-
maximal structural and catalytic stability within the pH-range 6.5-7.8
722937
10.4
-
4C, 2 h, 20% reduction in enzyme activity
722937
TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
30
-
T1/2: 18.1 h, at 30C
35
-
T1/2: 9.9 h, at 30C
40
-
stable below, T1/2: 5.9 h, at 30C
50
-
T1/2: 3.3 h, at 30C
60
-
T1/2: 1.9 h, at 30C
70
-
Tm-value is 70.1C. Retention of about 50% of its initial activity when heated for 60 min at 70.1C
Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
APPLICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
medicine