Rapid purification of secretory acid proteinase from Candida albicans and its characterization

Secretory acid proteinase from C. albicans was purified from culture supernatant to apparent homogeneity by ion-exchange chromatography. Two isozymes of the proteinase were resolved using a novel chromatofocusing method. The enzyme, which appears to be a glycoprotein, consists of a single polypeptide chain with glutamine at the N-terminus. Its molecular weight is about 45,000 and isoelectric point is pH 4.6. At pH 5, the proteinase is stable at 45 degrees C for at least 15 min. It has a broad substrate specificity. With BSA as a substrate, Km was determined to be 1.6 x 10(-4) M. The enzyme is inhibited by pepstatin and thus is a carboxyl proteinase. It undergoes autocatalytic digestion at or below pH 5.0. The kinetics of induction of proteinase by various proteins are also reported.