Comparative analysis of the human serine hydrolase OVCA2 to the model serine hydrolase homolog FSH1 from S. cerevisiae

Over 100 metabolic serine hydrolases are present in humans with confirmed functions in metabolism, immune response, and neurotransmission. Among potentially clinically-relevant but uncharacterized human serine hydrolases is OVCA2, a serine hydrolase that has been linked with a variety of cancer-related processes. Herein, we developed a heterologous expression system for OVCA2 and determined the comprehensive substrate specificity of OVCA2 against two ester substrate libraries. Based on this analysis, OVCA2 was confirmed as a serine hydrolase with a strong preference for long-chain alkyl ester substrates (>10-carbons) and high selectivity against a variety of short, branched, and substituted esters. Substitutional analysis was used to identify the catalytic residues of OVCA2 with a Ser117-His206-Asp179 classic catalytic triad. Comparison of the substrate specificity of OVCA2 to the model homologue FSH1 from Saccharomyces cerevisiae illustrated the tighter substrate selectivity of OVCA2, but their overlapping substrate preference for extended straight-chain alkyl esters. Conformation of the overlapping biochemical properties of OVCA2 and FSH1 was used to model structural information about OVCA2. Together our analysis provides detailed substrate specificity information about a previously, uncharacterized human serine hydrolase and begins to define the biological properties of OVCA2.