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Literature summary 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

Cloned(Commentary)

EC Number Cloned (Comment) Organism
2.1.1.5
-
 Homo sapiens

Crystallization (Commentary)

EC Number Crystallization (Comment) Organism
2.1.1.5 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

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

KM Value [mM]

EC Number KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
2.1.1.5 0.015
-
 L-homocysteine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
2.1.1.5 0.059
-
 betaine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
2.1.1.5 0.075
-
 betaine wild-type, pH 7.5, 37°C Homo sapiens
2.1.1.5 0.338
-
 L-homocysteine wild-type, pH 7.5, 37°C Homo sapiens
2.1.1.5 2.3
-
 L-homocysteine wild-type, cosubstrate S-methylmethionine, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
2.1.1.5 3.4
-
 S-methyl-L-methionine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens

Metals/Ions

EC Number Metals/Ions Comment Organism Structure
2.1.1.5 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

EC Number Organism UniProt Comment Textmining
2.1.1.5 Homo sapiens Q93088
-
-

Specific Activity [micromol/min/mg]

EC Number Specific Activity Minimum [µmol/min/mg] Specific Activity Maximum [µmol/min/mg] Comment Organism
2.1.1.5 2
-
 mutant G27S, pH 7.5, 37°C Homo sapiens
2.1.1.5 2
-
 mutant G27S, presence of 150 mM K+, pH 7.5, 37°C Homo sapiens
2.1.1.5 5
-
 mutant D26A, pH 7.5, 37°C Homo sapiens
2.1.1.5 18
-
 mutant D26A, presence of 150 mM K+, pH 7.5, 37°C Homo sapiens
2.1.1.5 100
-
 wild-type, pH 7.5, 37°C Homo sapiens
2.1.1.5 940
-
 wild-type, presence of 150 mM K+, pH 7.5, 37°C Homo sapiens

Substrates and Products (Substrate)

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

Turnover Number [1/s]

EC Number Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
2.1.1.5 0.0003
-
 L-homocysteine wild-type, cosubstrate S-methylmethionine, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
2.1.1.5 0.0044
-
 S-methyl-L-methionine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
2.1.1.5 0.0298
-
 betaine wild-type, pH 7.5, 37°C Homo sapiens
2.1.1.5 0.0367
-
 L-homocysteine wild-type, pH 7.5, 37°C Homo sapiens
2.1.1.5 0.0378
-
 L-homocysteine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
2.1.1.5 0.0422
-
 betaine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens

kcat/KM [mM/s]

EC Number kcat/KM Value [1/mMs-1] kcat/KM Value Maximum [1/mMs-1] Substrate Comment Organism Structure
2.1.1.5 0.108
-
 L-homocysteine wild-type, pH 7.5, 37°C Homo sapiens
2.1.1.5 0.386
-
 betaine wild-type, pH 7.5, 37°C Homo sapiens
2.1.1.5 0.716
-
 betaine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens
2.1.1.5 2.52
-
 L-homocysteine wild-type, presence of 150 mM KCl, pH 7.5, 37°C Homo sapiens