Benjaminiella poitrasii, a dimorphic zygomycetous fungus possesses three glutamate dehydrogenases, one requiring NAD while the other two use NADP as a coenzyme. In the activity staining after electrophoresis on native polyacrylamide gel NAD- dependent glutamate dehydrogenase revealed the presence of one enzyme that was expressed in both, yeast- and mycelium-form cells. While in case of NADP- dependent glutamate dehydrogenase two distinct activity bands that were differentially expressed in yeast- and mycelium-form cells were seen. Interestingly, during yeast-mycelium transition and reverse, quantitative changes in form-specific native NADP-dependent glutamate dehydrogenase activities were seen. The biochemical data on temperature and pH optima, thermostability, and kinetic properties confirmed the presence of two NADP-dependent proteins in B. poitrasii, parent strain. The monomorphic mutant (Y-5, yeast form) showed NADP- glutamate dehydrogenase similar to parent yeast-form enzyme. For the first time the significance of differential expression of these enzymes during morphological transition in B. poitrasii has been suggested.
