Purification and comparison of two forms of S-adenosyl-L-methionine synthetase from rat liver

Eur J Biochem. 1987 Dec 30;170(1-2):299-304. doi: 10.1111/j.1432-1033.1987.tb13699.x.


Only two S-adenosyl-L-methionine synthetase forms exist in rat liver: high-Mr S-adenosyl-L-methionine synthetase and low-Mr S-adenosyl-L-methionine synthetase, which have been purified to apparent homogeneity as judged by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. High-Mr S-adenosyl-L-methionine synthetase had an apparent molecular mass, determined by gel filtration, of 210 kDa and was a tetramer constituted by 48.5-kDa subunits, estimated by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The apparent molecular mass of low-Mr S-adenosyl-L-methionine synthetase, as estimated by gel filtration, was 110 kDa and was constituted by two subunits of 47 kDa. An antiserum against low-Mr S-adenosyl-L-methionine synthetase cross-reacted with the two forms. Reverse-phase HPLC runs of tryptic digestions of high-Mr and low-Mr S-adenosyl-L-methionine synthetase showed that the peptide maps of the two forms were very similar, if not identical. High-Mr S-adenosyl-L-methionine synthetase activity was inhibited by S-adenosyl-L-methionine and pyrophosphate. Depending on the dose used, S-adenosyl-L-methionine activated or inhibited low-Mr S-adenosyl-L-methionine synthetase and pyrophosphate had no effect on this form. The two synthetases showed a different specific activity at the physiological concentration of methionine. This report shows that even though the two forms are constructed of the same polypeptide chains, they are regulated in a different manner by methionine and by the products of the reaction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chromatography, Gel
  • Immunodiffusion
  • Isoenzymes / isolation & purification*
  • Isoenzymes / metabolism
  • Kinetics
  • Liver / enzymology*
  • Methionine Adenosyltransferase / isolation & purification*
  • Methionine Adenosyltransferase / metabolism
  • Peptide Mapping
  • Rats
  • Transferases / isolation & purification*


  • Isoenzymes
  • Transferases
  • Methionine Adenosyltransferase