Partial purification and characterization of methionine adenosyltransferase from pea seedlings

Methionine adenosyltransferase was partially purified from green shoots of 14-day-old pea seedlings. Recovery of the enzyme was improved by inclusion of the substrates MgATP and methionine in the extraction medium. Pea methionine adenosyltransferase has an absolute dependence on both divalent (Mg2+ or Mn2+) and monovalent (K+ or NH 4+ cations for activity. The Km value for methionine was 0.4 mM and for MgATP 0.3 mM. The enzyme activity was inhibited by tripolyphosphate and S-adenosyl-methionine.