Purification and characterization of a thermosensitive X-prolyl dipeptidyl aminopeptidase (dipeptidyl aminopeptidase yscV) from< i> Saccharomyces cerevisiae</i>

Abstract

Dipeptidyl aminopeptidase yscV, a heat-labile enzyme with X-prolyl dipeptidyl aminopeptidase activity, was purified about 470-fold from a protoplast lysate of Saccharomyces cerevisiae. The purification procedure included solubilization of tonoplast-bound activity by the non-ionic detergent octyl-β-d-glucopyranoside, glycerol gradient centrifugation and preparative isoelectric focusing. Sodium dodecyl sulfate polyacrylamide gel electrophoresis resulted in a single band for which a molecular weight of 40 000 was calculated. The peptidase was most active at pH 7.0–7.5 with as substrate. Substrate specificity studies indicate that the purified enzyme specifically hydrolyzes peptide bonds involving the carboxyl group of prolyl residues penultimate to unprotected termini unless arginine is the N-terminal amino acid. However, X-Ala-arylamide structures are not attacked. The actinomycete inhibitors antipain, chymostatin and pepstatin had no effect on the enzyme activity, but 5 mM phenylmethylsulfonyl fluoride, an inhibitor of serine peptidases, completely inhibited dipeptidyl aminopeptidase yscV activity. Some heavy metals (Ni2+, Cd2+, Zn2+, Hg2+) at a concentration of 5·10−4 M were also found to be potent inhibitors of enzyme activity.