Peptidase activities during morphogenesis of Mucor racemosus

Multiple peptidase activities are expressed in the dimorphic fungus Mucor racemosus. Peptide hydrolysis was measured using an enzyme-coupled colorimetric assay. Aminopeptidase as well as carboxypeptidase activities increased during spore, swollen spore, and budding yeast-to-hyphae conversions, and activities achieved a maximum level prior to the period of rapid germ tube formation. These increases in peptidase activity were prevented by cycloheximide. Three distinct aminopeptidases (AP) and three distinct carboxypeptidases (CP) were partially purified by gel filtration column chromatography. AP1 (235 kDa), AP2 (112 kDa), and AP3 (70 kDa) were all expressed in spore, yeast, and hyphae. The activity levels of AP2 and AP3 decreased in hyphae entering stationary growth. CP1 (250 kDa) and CP3 (50 kDa) activities were expressed exclusively in hyphae, whereas CP2 (77 kDa) was expressed in spore, yeast, and hyphal forms. CP1 activity was most pronounced in hyphae entering stationary growth. We concluded that M. racemosus expresses a multiplicity of peptidases and that CP1 and CP3 are morphology-specific carboxypeptidases.