REGULATION OF N-ACETYLGLUCOSAMINIDASE PRODUCTION IN CANDIDA-ALBICANS

The N-acetylglucosaminidase of Candida albicans is a secreted hydrolyt ic enzyme that contributes to the yeast's virulence. There was a signi ficant increase in the N-acetylglucosaminidase activity of C. albicans cells released from carbon starvation in medium containing N-acetylgl ucosamine. The increased enzyme activity in N-acetylglucosamine-grown cells correlated with increased transcription of the HEX1 gene, which encodes C. albicans N-acetylglucosaminidase. In contrast, glucose repr essed HEX1 transcription, and glucose-grown cells had on average 94-fo ld lower N-acetylglucosaminidase activities than did N-acetylglucosami ne-grown cells. N-acetylglucosaminidase induction in cells grown on N- acetylglucosamine was also repressed by fructose, mannose or galactose , although to a lesser extent than by glucose, and sucrose repressed e nzyme production by only 10%. Eighty-eight percent of the enzyme in N- acetylglucosamine-grown cells was localised in the periplasm, and afte r incubation for 5 h, 30 or 70% of the total enzyme activity was secre ted into the medium by yeast or mycelial cells, respectively. The cell ular location of the enzyme and the regulation of production by the ca rbon source indicate a scavenging role for C. albicans N-acetylglucosa minidase.