Exo-(l->3)- -glucanase, Autolysin and Trehalase Activities during Yeast Growth and Germ-tube Formation in Candida albicans

Abstract

Exo-(1 .fwdarw. 3)-.beta.-glucanase, .beta.-glucosidase, autolysin and trehalase were assayed in situ in C. albicans during yeast growth, starvation and germ-tube formation. Cell viability, germ-tube formation, intracellular glucose-6-phosphate dehydrogenase and .beta.-glucosidase were unaffected in cells incubated in 0.1 M-HCl for 15 min at 4.degree. C. However, in situ trehalase, (1 .fwdarw. 3)-.beta.-glucanase and autolysin activities in acid-treated cells decreased by 95, 50 and 35%, respectively, indicating that these enzymes are, in part, associated with the cell envelope. Trehalase activity increased throughout yeast growth and remained elevated during the 1st hour of incubation for germ-tube formation. All of the in situ trehalase activity in starved yeast cells could be measured without the permeabilizing treatment. .beta.-Glucosidase activity declined throughout yeast growth and did not alter during germ-tube formation. Both the (1 .fwdarw. 3)-.beta.-glucanase and autolysin activities were optimal at pH 5.6, inhibited by gluconolactone and HgCl2, and maximal at 15-16 h during yeast growth. Although autolysin activity increased by 50-100% when starved yeast cells were incubated for germ-tube formation, the in situ (1 .fwdarw. 3)-.beta.-glucanase remained constant. When acid-treated starved yeast cells were similarly induced, in situ (1 .fwdarw. 3)-.beta.-glucanase increased 100% over 3 h of germ-tube formation. Yeast cells secreted (1 .fwdarw. 3)-.beta.-glucanase into the growth medium. This was highest in early exponential phase cultures (34% of the maximum in situ activity) and declined throughout growth. (1 .fwdarw. 3)-.beta.-Glucanase was also secreted into the medium during germ-tube formation and this represented 80-100% of the in situ activity in germ-tube forming cells. Both secretion of (1 .fwdarw. 3)-.beta.-glucanase and germ-tube formation were inhibited by 2-deoxyglucose, ethidium bromide, trichodermin and azaserine.