Abstract:A novel serine carboxypeptidase gene CapA was identified in Aspergillus niger CBS 513.88 by screening based on genomic information and sequence alignment.The gene was cloned and expressed in Pichia pastoris.In shake flask cultures，the enzyme activity of recombinant strain GS115 （pPIC9K-CapA）reached 109.7 U/mL.The optimum temperature and pH of the enzyme was 45 ℃ and 6.0，respectively.After incubation at 30 ℃ to 50 ℃，or pH 4.0 to 8.0 for 1 h，more than 80% and 60%，respectively，of the initial enzyme activity was retained.Mg2+enhanced the activity of CapA.Cu2+，Fe2+，Co2+，and phenylmethylsulfonyl fluoride inhibited the activity.Among the six substrates tested，five were hydrolyzed by CapA.The broad substrate specificity of CapA included a preference for c-terminal hydrophobic amino acids leucine and lysine.The preferred substrate of CapA was N-carbobenzoxy-L-phenylalanyl-L-leucine.The demonstrated thermostability，pH stability，and hydrolysis characteristics of CapA could be valuable for food and biotechnology applications.