In vitro production of extracellular elastolytic proteinase by Histoplasma capsulatum var. duboisii and Histoplasma capsulatum var. capsulatum in the yeast phase.

Extracellular elastolytic proteinase was produced by yeast cultures of Histoplasma capsulatum var. duboisii and H. capsulatum var. capsulatum in three different induction media, assayed using elastin-orcein as the substrate. Medium-dependent variations in the time-course for enzyme production were observed and no peak was recorded. The proteinases hydrolysed both casein and bovine serum albumin indicating a broad substrate specificity. Both elastolytic proteinases had similar optimum pH (pH 8) and temperature (35 degrees C); over 90% residual elastolytic activity was measured in the crude enzymes of v. duboisii and v. capsulatum after incubation in the pH ranges 4.5-8.0 and 4.0-7.0 respectively, at 4 degrees C for 24 h. The proteinases were not significantly inhibited by any of the tested proteinase inhibitors. The molecular weights, estimated by column chromatography, were 23 kD. A probable role in the pathogenesis of histoplasmosis is discussed.