PURIFICATION AND CHARACTERIZATION OF THE ENDOGENOUS INHIBITOR FOR PROTEINASE-B FROM SCHIZOSACCHAROMYCES-POMBE

A rapid purification procedure for the endogenous inhibitor of protein ase 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 sys tem. The molecular mass of the purified polypeptide was estimated to b e 8100 Da by gel filtration. The isoelectric point of the inhibitor wa s 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 th e corresponding molecular mass 7370 Da. There are several differences in the molecular characteristics between the inhibitor from Schizosacc haromyces pombe and the corresponding inhibitor previously purified fr om Saccharomyces cerevisiae which might reflect the evolutionary diver gence between the two yeast genera.