Transport of basic amino acids in Candida albicans

Abstract

In Candida albicans, ATCC 46977, transport of basic amino acids is mediated by two systems (S₁ and S₂). Kinetic data and competitive inhibition studies of the different systems showed that transport of L-lysine, L-arginine and L-histidine have distinct specificities. System S₁ of L-lysine and L-arginine was highly specific for the respective single basic amino acid. However, S₂ of L-lysine and S₁ of L-histidine were shown to be specific systems for most of basic amino acids. S₂ of L-arginine was different from S₂ of L-lysine and S₁ of L-histidine. The effect of a thiol reagent, N-ethylmaleimide, revealed that S₂ of L-lysine and S₁ of L-histidine were sensitive to this reagent, while all other systems were insensitive. The transport activity of different systems of L-lysine, L-arginine and L-histidine was followed during the growth of C. albicans. It was observed that different basic amino-acid systems have maximum activity during different stages of C. albicans growth.