Identification of the polyamine N 8-acetyltransferase involved in the pathway of 1,3-diaminopropane production in Acanthamoeba culbertsoni

 A cytosolic polyamine N-acetyltransferase that preferentially catalyzes the acetylation of spermidine in the N ⁸-position was identified in the free-living pathogenic amoeba Acanthamoeba culbertsoni. In addition to spermidine, the enzyme also catalyzed the acetylation of spermine and putrescine with Michaelis constants (K _m values) of 97, 12, and 10 μM, respectively. The K _m value for acetylcoenzyme A (acetyl-CoA) was estimated to be 11 μM, whereas CoA had an inhibitory constant of 6 μM. The N-acetylase has a molecular mass of approximately 45 kDa. That the enzyme preferentially catalyzed the acetylation of spermidine at the N ⁸-position, resulting in N ⁸-acetylspermidine, the preferred substrate of the polyamine oxidase found in A. culbertsoni, indicates a role for the enzyme in the production of 1,3-diaminopropane, the major polyamine found in the Acanthamoeba. Received: 20 June 1995 / Accepted: 16 September 1995