Purification and Characterization of Phospholipase B from Candida utilis

Abstract

Phospholipase B (PLB) from the asporogenous yeast Candida utilis was purified to homogeneity from a culture broth. The apparent molecular mass was 90–110 kDa by SDS–PAGE. The enzyme had two pH optima, one acidic (pH 3.0) and the other alkaline (pH 7.5). At acidic pH the enzyme hydrolyzed all phospholipids tested without metal ions. On the other hand, the PLB showed substrate specificity and required metal ions for alkaline activity.
The cDNA sequence of the PLB was analyzed by a combination of several PCR procedures. The PLB encoded a protein consisting of 643 amino acids. The amino acid sequence contained a lipase consensus sequence (GxSxG) and catalytic arginine and aspartic acid motifs which were identified as the catalytic triad in the PLB from Kluyveromyces lactis, suggesting that the catalytic mechanism of the PLB is similar to that of cytosolic phospholipase A₂ (cPLA₂), found in mammalian tissues.