A keratinolytic proteinase secreted by Microsporum canis in a broth containing human hair was purified 134-fold from the culture filtrate by ion-exchange chromatography using DEAE-Sephacel, CM-Sephadex C-50, and by Sephadex G-75 gel filtration. The purified enzyme was electrophoretically homogeneous with a molecular weight of 33,000. The enzyme had an optimum pH of 8.0, and the activity was stable in the alkaline pH range. Enzyme activity increased with temperature up to 35 degrees C and was stable up to 45 degrees C. The keratinolytic activity was not affected by the addition of nonionic detergents, was activated by Mg2+, but inhibited by Zn2+. The purified enzyme was used to obtain guinea pig antiserum. The antiserum tested by double diffusion against the purified enzyme showed a single line of precipitation and completely neutralized the proteinase activity. This study reaffirms that the proteinase from M. canis may be a biochemical mechanism for the invasion of keratinized tissue, and could possibly play a role in the hypersensitivity reactions arising from superficial infections of this fungus.
Microsporum/enzymology* ; Peptide Hydrolases/isolation & purification*