ENZYMATIC AMINOPROPYLATION OF CERTAIN SECONDARY-AMINES

Two unusual aminopropyl accepters found in a survey of putrescine bind ing sites of mammalian spermidine synthase, N-methylputrescine (I) and 4-aminomethylpiperidine (II), were examined for their aminopropyl der ivatives. Studies under in vitro incubation conditions suggested that the aminopropyl derivatives of the secondary amine of I and II, N-4-me thylspermidine (Is) and 1-N-(3-aminopropyl)-4-aminomethylpiperidine (I Is), and of the primary amine of I and II, N-8-methylspermidine (Ip) a nd 4-[N-(3-aminopropyl)aminomethyl]piperidine (IIp), respectively, wer e biosynthesized by rat spermidine synthase. Studies on the cell cultu re system of cultured rat hepatoma (HTC) cells treated with alpha-difl uoromethylornithine, an ornithine decarboxylase inhibitor, clearly sho wed the presence of Is and Ip when I was administered, and IIs and IIp when II was administered, with no detection of putrescine or spermidi ne. These results suggested that mammalian spermidine synthase can tra nsfer the aminopropyl moiety of decarboxylated S-adenosylmethionine to certain secondary amines in Living cells.