CHANGES IN GLUTATHIONE METABOLIC ENZYMES DURING YEAST-TO-MYCELIUM CONVERSION OF CANDIDA-ALBICANS

Candida albicans is a dimorphic yeast capable of producing alternate m orphological forms (yeast or mycelium) in response to environmental ch anges. The intracellular level of glutathione, which helps to maintain the redox potential of the cell, is decreased significantly during th e thermal induction of yeast-to-mycelium conversion. The reason for th e decline of glutathione in the mycelial form is not understood. We ha ve, therefore investigated the levels of glutathione reductase, glutat hione S-transferase, gamma-glutamyltranspeptidase, and glutathione per oxidase, four key enzymes involved in glutathione metabolism, in the y east and mycelial forms. Yeast cells of C. albicans 3153A Lee's induce d in Lee's medium (pH 6.5) at 37 degrees C for 3 h to produce germ tub es. Cell lysates were prepared from yeast and mycelial cells, and glut athione reductase, glutathione S-transferase. gamma-glutamyltranspepti dase and glutathione peroxidase were assayed spectrophotometrically. T here was a 640% increase of the level of gamma-glutamyltranspeptidase in the germ tubes as compared with the yeast cells. No other significa nt alteration of the levels of enzymes was noted. This increased activ ity of gamma-glutamyltranspeptidase, which cleaves the glutamic acid r esidue of glutathione (Glu-Cys-Gly) appears to be, at least in part, r esponsible for the rapid decrease of the intracellular glutathione in C. albicans during the yeast-to-mycelium conversion.