M. Manavathu et al., CHANGES IN GLUTATHIONE METABOLIC ENZYMES DURING YEAST-TO-MYCELIUM CONVERSION OF CANDIDA-ALBICANS, Canadian journal of microbiology, 42(1), 1996, pp. 76-79
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.