IDENTIFICATION OF THE POLYAMINE N-8-ACETYLTRANSFERASE INVOLVED IN THEPATHWAY OF 1,3-DIAMINOPROPANE PRODUCTION IN ACANTHAMOEBA-CULBERTSONI

A cytosolic polyamine N-acetyltransferase that preferentially catalyze s the acetylation of spermidine in the N-8-position was identified in the free-living pathogenic amoeba Acanthamoeba culbertsoni. In additio n to spermidine, the enzyme also catalyzed the acetylation of spermine and putrescine with Michaelis constants (K-m values) of 97, 12, and 1 0 mu M, respectively. The K-m value for acetylcoenzyme A (acetyl-CoA) was estimated to be 11 mu M, whereas CoA had an inhibitory constant of 6 mu M. The N-acetylase has a molecular mass of approximately 45 kDa. That the enzyme preferentially catalyzed the acetylation of spermidin e at the N-8-position, resulting in N-8-acetylspermidine, the preferre d substrate of the polyamine oxidase found in A. culbertsoni, indicate s a role for the enzyme in the production of 1,3-diaminopropane, the m ajor polyamine found in the Acanthamoeba.