Confirmation of a ping-pong mechanism for S-adenosyl-L-methionine:magnesium protoporphyrin methyltransferase of etiolated wheat by an exchange reaction

Biochem Biophys Res Commun. 1989 Jul 14;162(1):483-90. doi: 10.1016/0006-291x(89)92023-8.


An exchange reaction between unlabeled S-adenosyl-L-methionine and radiolabeled S-adenosyl-L-homocysteine has been used to confirm the occurrence of a ping-pong mechanism in S-adenosyl-L-methionine:magnesium protoporphyrin methyltransferase of etiolated wheat. The enzyme, S-adenosyl-L-homocysteine hydrolase, has been used to prepare radiolabeled S-adenosyl-L-homocysteine from labeled adenosine and DL-homocysteine. The exchange reaction was accomplished with a methyltransferase preparation purified by affinity chromatography on hemin-linked Sepharose 4B, and radioactivity was exchanged into unlabeled S-adenosyl-L-methionine to an extent of 70% of the theoretical maximum value.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, Affinity
  • Chromatography, Ion Exchange
  • Kinetics
  • Methyltransferases / isolation & purification*
  • Oxygenases
  • S-Adenosylhomocysteine / chemical synthesis
  • S-Adenosylmethionine
  • Triticum / enzymology*


  • S-Adenosylmethionine
  • S-Adenosylhomocysteine
  • Oxygenases
  • magnesium protoporphyrin monomethyl ester oxidative cyclase
  • Methyltransferases
  • magnesium-protoporphyrin methyltransferase