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Literature summary for 2.1.1.5 extracted from

  • Mladkova, J.; Hladilkova, J.; Diamond, C.E.; Tryon, K.; Yamada, K.; Garrow, T.A.; Jungwirth, P.; Koutmos, M.; Jiracek, J.
    Specific potassium ion interactions facilitate homocysteine binding to betaine-homocysteine S-methyltransferase (2014), Proteins, 82, 2552-2564.
    View publication on PubMed
Search for more literature for 2.1.1.5

Cloned(Commentary)

Cloned (Comment) Organism
-
 Homo sapiens

Crystallization (Commentary)

Crystallization (Comment) Organism
molecular dynamics simulations predict that K+ ions interact with residues Asp26 and/or Glu159. Crystal structure of BHMT bound to homocysteine confirms these sites of interaction and reveals further contacts between K+ ions and BHMT residues Gly27, Gln72, Gln247, and Gly298 Homo sapiens

Protein Variants

Protein Variants Comment Organism
D26A almost 3fold decrease in stimulation by K+ Homo sapiens
E159A complete loss of activity Homo sapiens
E159Q complete loss of activity Homo sapiens
G27S no stimulation by K+ Homo sapiens
G28S very small decrease in stimulation by K+ Homo sapiens

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
0.015
-
 L-homocysteine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
0.059
-
 betaine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
0.075
-
 betaine wild-type, pH 7.5, 37°C Homo sapiens
0.338
-
 L-homocysteine wild-type, pH 7.5, 37°C Homo sapiens
2.3
-
 L-homocysteine wild-type, cosubstrate S-methylmethionine, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
3.4
-
 S-methyl-L-methionine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens

Metals/Ions

Metals/Ions Comment Organism Structure
K+ Km value around 0.1 mM. The presence of potassium ions lowers the apparent KM of the enzyme for homocysteine, but it does not affect the apparent KM for betaine or the apparent kcat for either substrate Homo sapiens

Organism

Organism UniProt Comment Textmining
Homo sapiens Q93088
-
-

Specific Activity [micromol/min/mg]

Specific Activity Minimum [µmol/min/mg] Specific Activity Maximum [µmol/min/mg] Comment Organism
2
-
 mutant G27S, pH 7.5, 37°C Homo sapiens
2
-
 mutant G27S, presence of 150 mM K+, pH 7.5, 37°C Homo sapiens
5
-
 mutant D26A, pH 7.5, 37°C Homo sapiens
18
-
 mutant D26A, presence of 150 mM K+, pH 7.5, 37°C Homo sapiens
100
-
 wild-type, pH 7.5, 37°C Homo sapiens
940
-
 wild-type, presence of 150 mM K+, pH 7.5, 37°C Homo sapiens

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
L-homocysteine + betaine
-
 Homo sapiens L-methionine + dimethylglycine
-
 ?
L-homocysteine + S-methyl-L-methionine
-
 Homo sapiens 2 L-methionine
-
 ?

Turnover Number [1/s]

Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
0.0003
-
 L-homocysteine wild-type, cosubstrate S-methylmethionine, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
0.0044
-
 S-methyl-L-methionine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
0.0298
-
 betaine wild-type, pH 7.5, 37°C Homo sapiens
0.0367
-
 L-homocysteine wild-type, pH 7.5, 37°C Homo sapiens
0.0378
-
 L-homocysteine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
0.0422
-
 betaine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens

kcat/KM [mM/s]

kcat/KM Value [1/mMs-1] kcat/KM Value Maximum [1/mMs-1] Substrate Comment Organism Structure
0.108
-
 L-homocysteine wild-type, pH 7.5, 37°C Homo sapiens
0.386
-
 betaine wild-type, pH 7.5, 37°C Homo sapiens
0.716
-
 betaine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
2.52
-
 L-homocysteine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens