Functional expression and characterization of a novel aminopeptidase B from in .

A novel aminopeptidase B (APB-AN) was identified from CGMCC 3.1454 for the first time and was cloned and expressed in . The mature enzyme of approximately 100 kDa was purified for characterization. The optimum pH and temperature of the recombinant APB-AN were determined to be 7.0 and 40 °C, respectively. The enzyme was stable below 40 °C and at pH values from 5.0 to 8.0. The and values were determined to be 0.61 mmol/L and 11.45 mmol/L/min, respectively, using Arg-NA as the substrate. APB-AN was inhibited by Cu and Fe and activated by Co and Na. Most metal chelators (Ca, Mg and Mn) and aminopeptidase inhibitors (bestatin and puromycin) suppressed its activity. APB-AN was found to be active towards 13 kinds of amino acid -nitroanilide (NA) substrates:Arg-NA, Lys-NA, Tyr- pNA, Trp-NA, Phe-NA, His-NA, Ala-NA, Met-NA, Leu-NA, Glu-NA, Val-NA, Pro-NA and Ile-NA, and the most preferred N-terminal amino acids were arginine and lysine. APB-AN also hydrolyzed 4 natural proteins: casein, bovine serum albumin, soy protein isolate and water-soluble wheat protein. It is expected that APB-AN has potential food processing applications.