Enzymatic Properties of the Recombinant Serine-Type Carboxypeptidase OcpC, Which Is Unique to Aspergillus oryzae

Gene AO090103000153 is unique to Aspergillus oryzae RIB40 and A. flavus NRRL3357, and is speculated to encode a serine-type carboxypeptidase. In this study, we purified and characterized a heterologously expressed gene product of AO090103000153. 5′-Rapid amplification of cDNA ends indicated that the translation start site of the gene is located 1,586 bp downstream of the translation start site predicted by the genome sequencing project. The gene, starting from the revised translation start codon, termed ocpC, was transcribed constantly in A. oryzae RIB40. Purified recombinant OcpC exhibited the enzymatic properties of a serine-type carboxypeptidase. This protease was stable at temperatures below 45 °C and a low pH, and had broad substrate specificity for N-acylpeptides, but it exhibited significantly lower specific activity and a lower k cat value for substrates than previously reported serine-type carboxypeptidases from A. oryzae.