Confirmation of a ping-pong mechanism for S-adenosyl-L-methionine:magnesium protoporphyrin methyltransferase of etiolated wheat by an exchange reaction |
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Authors: | W C Yee S J Eglsaer W R Richards |
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Institution: | Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada. |
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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. |
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