Potential inhibitors of S-adenosylmethionine-dependent methyltransferases. 7. Role of the ribosyl moiety in enzymatic binding of S-adenosyl-L-homocysteine and S-adenosyl-L-methionine.

A series of 2',3'-acyclic analogues of S-adenosyl-L-homocysteine were synthesized and evaluated as inhibitors of S-adenosyl-L-methionine-dependent methyltransferases. The 2',3'-acyclic analogues were prepared by periodate oxidation of the corresponding ribonucleosides, followed by reduction of the intermediate dialdehydes with sodium borohydride. These 2',3'-acyclic ribonucleosides were inactive as inhibitors of histamine N-methyltransferase, catechol O-methyltransferase, phenylethanolamine N-methyltransferase, and hydroxyindole O-methyltransferase. These results suggest that the rigidity of the ribosyl ring of S-adenosyl-L-homocysteine is crucial to its enzymatic bindings.