POLYAMINE N-ACETYLTRANSFERASE IN LEISHMANIA-AMAZONENSIS

N-Acetyltransferase, which is suggested to be responsible for the prod uction of N-1-acetylspermidine in Leishmania amazonensis and to be inv olved in the process of inactivation and degradation of excessive poly amines, was partially purified and characterized. Among the substrates tested, sym-norspermidine, sym-norspermine, and 1,3-diaminopropane ha d the highest reaction rates, but the naturally occurring polyamines s permine and spermidine were also acetylated at considerable rates, whe reas putrescine was a poor substrate. The Michaelis constants (K-m val ues) for spermine and spermidine were 0.66 and 3.3 mM, respectively. T he K-m value for acetylcoenzyme A (acetyl-CoA) was determined to be 34 mu M. CoA inhibited the reaction in a competitive manner; the inhibit ion constant was 5 mu M. The enzyme showed an apparent relative molecu lar mass of 35,000.