Purification and characterization of the endogenous inhibitor for proteinase B from Schizosaccharomyces pombe.

A rapid purification procedure for the endogenous inhibitor of proteinase yspB from Schizosaccharomyces pombe is described. Starting from a boiled extract, the purification procedure included an ionic exchange chromatography and two reverse phase chromatographies using a HPLC system. The molecular mass of the purified polypeptide was estimated to be 8,100 Da by gel filtration. The isoelectric point of the inhibitor was found to be 5.3 after electrofocusing of a purified preparation. The amino acid composition of the proteinase yspB inhibitor was analyzed after acid hydrolysis. The calculated number of residues was 67 and the corresponding molecular mass 7370 Da. There are several differences in the molecular characteristics between the inhibitor from Schizosaccharomyces pombe and the corresponding inhibitor previously purified from Saccharomyces cerevisiae which might reflect the evolutionary divergence between the two yeast genera.