Evidence for arylamine N-acetyltransferase activity in the fungi Candida albicans

Abstract

N-acetyltransferase activities were determined in Candida albicans, which is a member of the normal flora of the mucous membranes in the respiratory, gastrointestinal and female genital tract. The N-acetylation of 2-aminofluorene and p-aminobenzoic acid by the N-acetyltransferase from Candida albicans was determined using high pressure liquid chromatography. The activities (mean±S.D.) of N-acetyltransferase from Candida albicans cytosols were 1.06±0.01 nmol/min per mg protein for the acetylation of 2-aminofluorene substrate, and not detectable levels of acetyl- p-aminobenzoic acid for the acetylation of p-aminobenzoic acid. The apparent kinetic constants K m and V max values were 0.17±0.06 mM and 1.43±0.42 nmol/min per mg protein, respectively, for 2-aminofluorene substrate. The optimum pH value for the enzyme activity was 8.0. The optimal temperature for the enzyme activity is 40°C for 2-aminofluorene substrate. Among a series of divalent cations and salts, Fe 2+, SCN −, I −, and NH 4+ were demonstrated to be the most potent inhibitors. The N-acetyltransferase activity was inhibited by iodoacetamide: at 0.25 mM iodoacetamide, activity was reduced 50% and 1.0 mM iodoacetamide inhibited activity more than 90%. This is the first demonstration of acetyl CoA arylamine N-acetyltransferase activity in the yeast-like fungus Candida albicans.