Ligand L-homocysteine

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Basic Ligand Information

Molecular Structure
Picture of L-homocysteine (click for magnification)
Molecular Formula
BRENDA Name
InChIKey
C4H9NO2S
L-homocysteine
FFFHZYDWPBMWHY-VKHMYHEASA-N
Synonyms:
(S)-2-amino-4-mercaptobutanoic acid, homocysteine


Show all pahtways known for Show all BRENDA pathways known for L-homocysteine

Roles as Enzyme Ligand

In Vivo Substrate in Enzyme-catalyzed Reactions (23 results)

EC NUMBER
PROVEN IN VIVO REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
dimethylthetin + L-homocysteine = S-methylthioglycolate + L-methionine
show the reaction diagram
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L-homocysteine + H2O = hydrogen sulfide + NH3 + 2-oxobutanoate
show the reaction diagram
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ATP + L-homocysteine + tRNAMet = ?
show the reaction diagram
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In Vivo Product in Enzyme-catalyzed Reactions (19 results)

EC NUMBER
PROVEN IN VIVO REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
GSH + homocystine = GSSG + homocysteine
show the reaction diagram
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L-methionine + nicotinamide = L-homocysteine + 1-methylnicotinamide
show the reaction diagram
-
-
L-cystathionine + acetate = O-acetyl-L-serine + L-homocysteine
show the reaction diagram
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-
L-homocysteine-thiolactone + H2O = L-homocysteine
show the reaction diagram
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-
L-cystathionine + H2O = L-homocysteine + pyruvate + NH3
show the reaction diagram
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-
L-cystathionine + H2O = L-homocysteine + pyruvate + NH3
show the reaction diagram
-
-

Substrate in Enzyme-catalyzed Reactions (171 results)

EC NUMBER
REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
L-homocysteine + H2O + O2 = 4-thio-2-ketobutyric acid + NH3 + H2O2
show the reaction diagram
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sulfide + homocysteine + coenzyme Q1 = homocysteine persulfide + reduced coenzyme Q1
show the reaction diagram
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hydrogen sulfide + homocysteine + coenzyme Q1 = ?
show the reaction diagram
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dimethylthetin + L-homocysteine = S-methylthioglycolate + L-methionine
show the reaction diagram
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L-homocysteine + KCN = gamma-cyano-alpha-aminobutyric acid + H2S
show the reaction diagram
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2-oxosuccinamic acid + L-homocysteine = L-asparagine + 4-mercapto-2-oxobutanoate
show the reaction diagram
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L-homocysteine + phenylpyruvate = 4-mercapto-2-oxobutanoate + L-phenylalanine
show the reaction diagram
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3-mercaptopyruvate + L-homocysteine = ?
show the reaction diagram
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L-homocysteine + H2O = ?
show the reaction diagram
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L-Homocysteine = D-Homocysteine
show the reaction diagram
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ATP + L-homocysteine + tRNAMet = ?
show the reaction diagram
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ATP + L-Glu + L-homocysteine = ADP + phosphate + gamma-L-Glu-L-homocysteine
show the reaction diagram
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L-2-aminoadipate + L-homocysteine + L-valine + ATP = N-(5-amino-5-carboxypentanoyl)-L-homocysteinyl-D-valine + AMP + diphosphate
show the reaction diagram
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Product in Enzyme-catalyzed Reactions (49 results)

EC NUMBER
REACTION
REACTION DIAGRAM
LITERATURE
ENZYME 3D STRUCTURE
L-methionine + nicotinamide = L-homocysteine + 1-methylnicotinamide
show the reaction diagram
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S-adenosyl-L-methionine + adenine in 5'-UACACUCGAUCU-GGACU-AAAGCUGCUC = homocysteine + 5'-UACACUCGAUCU-GG-(N6-methyl)ACU-AAAGCUGCUC
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L-cystathionine + acetate = O-acetyl-L-serine + L-homocysteine
show the reaction diagram
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-
O-acetylhomoserine + H2S = homocysteine + ?
show the reaction diagram
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homocysteinethiolactone + H2O = homocysteine
show the reaction diagram
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L-homocysteine-thiolactone + H2O = L-homocysteine
show the reaction diagram
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L-cystathionine + H2O = L-homocysteine + pyruvate + NH3
show the reaction diagram
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Activator in Enzyme-catalyzed Reactions (10 results)

EC NUMBER
COMMENTARY
LITERATURE
ENZYME 3D STRUCTURE
treatment of cells results in increase in enzyme mRNA and protein
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induces reaction
can replace 2-mercaptoethanol
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10 fold activation
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protection against inactivation by arabinosyl adenine
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induces the enzyme activation 2.5fold and 4fold in endothelial progenitor cells at 0.1 mM and 0.2 mM, respectively. Vitamin B6, and B9 significantly impair homocysteine-mediated EPC caspase-3 activation in vitro, and inhibitor N-carbobenzyloxy-VAD-fluoromethyl ketone highly reduces the activating effect, overview
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induces the enzyme activation 3.5fold in endothelial progenitor cells at 0.2 mM
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homocysteine activates matrix metalloproteinase-9, muscimol ameliorates the homocysteine-mediated MMP-9 activation
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Inhibitor in Enzyme-catalyzed Reactions (51 results)

EC NUMBER
COMMENTARY
LITERATURE
ENZYME 3D STRUCTURE
GPx-1 is inhibited by 0.05-0.5 mM homocysteine, especially at low glutathione concentrations
-
in the reverse reaction
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at 0.005 mM 12% inactivation after 1 h incubation
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competitive to sulfide
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noncompetitive with respect to substrate, competitive with regard to pyridoxal 5'-phosphate
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irreversible in the presence of O2 and high pH
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strong
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slight
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uncompetitive vs. O-acetyl-L-serine, noncompetitive vs. chloroalanine and L-cysteine
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reacts with pyridoxal 5'-phosphate to yield thiazolidine derivative
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-
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poor
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inhibtory effect is reversed by alanine
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3D Structure of Enzyme-Ligand-Complex (PDB) (27 results)

Enzyme Kinetic Parameters

kcat Value (Turnover Number) (57 results)

EC NUMBER
TURNOVER NUMBER [1/S]
TURNOVER NUMBER MAXIMUM [1/S]
COMMENTARY
LITERATURE
92
-
pH 7.4, 25C
0.38
-
pH 6, 30C, cosubstrate: S-adenosyl-L-methionine
0.38
-
with [methyl-14C]S-adenosyl-L-methionine, pH 6.5, 30C
0.8
-
in 200 mM of HEPES, pH 7.4, at 37C
1.7
-
pH 8.0, 37C
0.00139
-
pH 7.0, 35C

KM Value (138 results)

EC NUMBER
KM VALUE [MM]
KM VALUE MAXIMUM [MM]
COMMENTARY
LITERATURE
1.3
-
-
22
-
pH 7.4, 25C
22
-
at pH 7.4 and 37C
4.17
-
at 45C, pH 7.5
24.7
-
cosubstrate 2-oxosuccinamate
12.5
-
in 200 mM of HEPES, pH 7.4, at 37C

Ki Value (13 results)

EC NUMBER
KI VALUE [MM]
KI VALUE MAXIMUM [MM]
COMMENTARY
LITERATURE
10
-
-
0.224
-
-
4
-
pH 7.8, 37C

IC50 Value (1 result)

EC NUMBER
IC50 VALUE
IC50 VALUE MAXIMUM
COMMENTARY
LITERATURE
0.727
-
recombinant enzyme

References & Links

Links to other databases for L-homocysteine

ChEBI
PubChem
ChEBI
PubChem