ARGININE AMINOPEPTIDASE, AN INTEGRAL MEMBRANE-PROTEIN OF THE CRYPTOSPORIDIUM-PARVUM SPOROZOITE

Cryptosporidium parvum oocysts were studied for the expression of amin opeptidase by using amino at:ids bound to the synthetic fluorescent su bstrate 7-amino-4-trifluoromethyl coumarin. After 1 h of incubation, i ntact oocysts showed no activity; however, homogenization and solubili zation with Triton X-114 followed, by phase separation yielded a 22-fo ld increase in aminopeptidase activity in the detergent fraction. With arginyl-6-amino-2-styrylquinoline as a substrate, aminopeptidase acti vity was observed in permeabilized oocysts and freshly excysted sporoz oites but not on intact oocysts or empty oocyst membranes after excyst ation. These results suggest that C. parvum expresses an arginine amin opeptidase that is an integral protein of the sporozoite membrane.