REAFFIRMATION THAT METABOLISM OF POLYAMINES BY BOVINE PLASMA AMINE OXIDASE OCCURS STRICTLY AT THE PRIMARY AMINO TERMINI

Oxidation of the biologically important polyamines spermine and spermi dine by plasma amine oxidase (PAO) was specified many years ago to occ ur at the terminal primary rather than internal secondary amine positi ons. However, the finding of sequential enzymatic conversion of spermi ne to spermidine and then to putrescine (1,4-butanediamine) is superfi cially suggestive of metabolism at the secondary amine positions, and a recent publication (Houen, G., Beck, K., and Jensen, A. L. (1994) Ac ta Chem. Scand 48, 52-60) claimed that the original interpretation of preferential ''terminal'' deamination does not stand up to scrutiny wi th modern methods of analysis. We herein demonstrate that the findings cited in support of secondary amine deamination can arise artifactual ly from spontaneous elimination/addition reactions following initial m etabolism at the terminal positions of 3-(aminopropyl)amines. We furth er find no evidence for the ability of PAO to metabolize the secondary amine position in homospermidine, which is devoid of such complicatin g side reactions. Our results support the original claimed specificity of PAO for the primary amino termini of polyamines, all of which are consistent with the general finding that the quinone-dependent copper amine oxidases specifically metabolize primary amines.