Dimorphism in Benjaminiella poitrasii: involvement of intracellular endochitinase and N-acetylglucosaminidase activities in the yeast-mycelium transition.
The chitinase and N-acetylglucosaminidase activities in cell-wall-bound and free fractions in the dimorphic fungus Benjaminiella poitrasii were studied as a function of morphological (unicellular yeast-mycelium) transition. The specific activities of chitinases of cell-wall-free, particularly in the membrane fraction, were significantly different in the yeast and mycelial forms. During the yeast-mycelium transition, the N-acetylglucosaminidase activity isolated in a membrane preparation increased steadily. The activity of the yeast cells (0.83 +/- 0.17 nkat/mg protein) increased 17-fold to 14.2 +/- 1.7 nkat/mg protein in 1-d-old mycelial cells. The endochitinase activity increased 12-fold between 6 and 12 h and thereafter practically remained unchanged up to 24 h. A reverse trend in the chitinolytic activities was observed during the mycelium-yeast transition. Isoelectrofocussing (pH range 3.5-10) of mixed membrane fraction free of particulate fraction of parent and morphological (Y-5, yeast-form) mutant cells separated endochitinase and N-acetylglucosaminidase activity into two pH ranges, viz. 4.3-5.7 and 6.1-7.7, respectively. The predominant N-acetylglucosaminidase activity observed at pH 6.9 and 7.1 for the parent strain membrane fraction was undetected in the mutant preparation. The results suggested that the membrane-bound (either tightly or loosely) chitinolytic enzymes, particularly, N-acetylglucosaminidase, significantly contributed to the morphological changes in B. poitrasii.
Ghormade
V S
VS
Biochemical Sciences Division, National Chemical Laboratory, Pune-411008, India.
Lachke
S A
SA
Deshpande
M V
MV
D000118:Acetylglucosaminidase / Q000378:metabolism*; D002688:Chitinases / Q000378:metabolism*; D003470:Culture Media; D005658:Fungi / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development*; D007525:Isoelectric Focusing; D013347:Subcellular Fractions / Q000378:metabolism
D003470:Culture Media; D002688:Chitinases; D000118:Acetylglucosaminidase