MetaCyc Enzyme: S-adenosylmethionine synthetase

Gene: SAMS1 Accession Number: G-9126 (MetaCyc)

Species: Catharanthus roseus

SAM synthetase is encoded by a small gene family of three members in C. roseus. The three genes are differentially expressed in seedlings, and in cell cultures treated with salt stress, nutrient stress and fungal elicitor. The three isoenzymes however have similar properties such as subcellular location, protein size, Kms for substrates, optimum pH and temperature, dependence on cations, inhibition by end products and other metabolites.

Locations: cytoplasm

Molecular Weight of Polypeptide: 45 kD (experimental) [Schroder97 ]

Relationship Links: Entrez-Nucleotide:PART-OF:Z71271

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

GO Terms:

Cellular Component: GO:0005737 - cytoplasm [Schroder97]

Enzymatic reaction of: S-adenosylmethionine synthetase

Synonyms: methionine adenosyltransferase

EC Number:

ATP + L-methionine + H2O <=> S-adenosyl-L-methionine + phosphate + diphosphate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

The reaction is favored in the direction shown.

In Pathways: S-adenosyl-L-methionine cycle II

The enzyme is strictly dependent on divalent cations such as Mg2+, Mn2+ and Co2+. It also requires monovalent cations, such as K+, NH4+, for optimum activity. The reaction intermediate, PPPi, is a strong inhibitor with Ki of 35 uM.

Cofactors or Prosthetic Groups: Co2+ [Schroder97], Mn2+ [Schroder97], Mg2+ [Schroder97]

Activators (Unknown Mechanism): K+ [Schroder97] , ammonium [Schroder97]

Inhibitors (Unknown Mechanism): PPPi [Schroder97] , S-adenosyl-L-methionine [Schroder97] , diphosphate [Schroder97] , phosphate [Schroder97] , GTP [Schroder97] , CTP [Schroder97] , ADP [Schroder97] , cycloleucine [Schroder97] , L-ethionine [Schroder97]

Primary Physiological Regulators of Enzyme Activity: PPPi , S-adenosyl-L-methionine , diphosphate , phosphate

Kinetic Parameters:

Km (μM)

T(opt): 37-45 °C [Schroder97]

pH(opt): 7-8.3 [Schroder97]


Schroder97: Schroder G, Eichel J, Breinig S, Schroder J (1997). "Three differentially expressed S-adenosylmethionine synthetases from Catharanthus roseus: molecular and functional characterization." Plant Mol Biol 33(2);211-22. PMID: 9037140

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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