Abstract
Yeast carboxypeptidase Y (CPY) is a serine protease with broad substrate specificity. Structurally, CPY belongs to the α/β hydrolase fold family and contains characteristic large helices, termed the V-shape helix, above the active site cavity. Four intramolecular disulfide bonds are located in and around the V-shape helix. In this study, mutant CPYs were constructed in which one of these disulfide bonds was disrupted. Mutants lacking the C193-C207 bond located at the beginning of the V-shape helix aggregated easily, while mutants lacking the C262-C268 bond located at the end of the V-shape helix displayed decreased hydrolytic activity. The results indicate that the V-shape helix is involved in CPY catalysis and in maintenance of its conformation.