An enzyme activity located in the soluble fraction of rat liver which is known to deacetylate N8-acetylspermidine is studied. Using a crude cytosol preparation from rat liver, tritium-labelled N8-acetylspermidine [acetyl-3H] was shown to undergo deacetylation which was dependent upon both time of incubation and protein concentration. The Michalis constant for this deacetylation of N8-acetylspermidine is approximately 4.4 μM.
N1-Acetylspermidine showed a competitive inhibition of this N8-acetylspermidine deacetylation activity, and was found to be the most potent inhibitor tested. Diamine and polyamine compounds were also shown to inhibit the deacetylation of N8-acetylspermidine. Spermidine was the most potent inhibitor of the naturally occurring polyamines tested, followed in order by spermine, putrescine, and cadaverine. Of numerous acetylated compounds studied, only acetylprocainamide showed any inhibition of this N8-acetylspermidine deacetylating activity at concentrations below 10.0 mM.
The possible functions of the deacetylating activity are discussed along the speculatio of the role this enzyme activity may play in vivo
