title: Confirmation of a ping-pong mechanism for S-adenosyl-L-methionine:magnesium protoporphyrin methyltransferase of etiolated wheat by an exchange reaction.
abstract: 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.
authors.affiliation: Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: W C
authors.initials: WC
authors.lastname: Yee
authors.forename: S J
authors.initials: SJ
authors.lastname: Eglsaer
authors.forename: W R
authors.initials: WR
authors.lastname: Richards
mesh_terms: D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D007700:Kinetics; D008780:Methyltransferases / Q000302:isolation & purification*; D010105:Oxygenases; D012435:S-Adenosylhomocysteine / Q000138:chemical synthesis; D012436:S-Adenosylmethionine; D014908:Triticum / Q000201:enzymology*
chemical_list: D012436:S-Adenosylmethionine; D012435:S-Adenosylhomocysteine; D010105:Oxygenases; C053161:magnesium protoporphyrin monomethyl ester oxidative cyclase; D008780:Methyltransferases; C060234:magnesium-protoporphyrin methyltransferase