A dual-functional aminopeptidase from Streptomyces canus T20 and its application in the preparation of small rice peptides

Abstract

An aminopeptidase that derived from Streptomyces canus T20 (ScAP) was successfully expressed and characterized in Escherichia coli BL21 (DE3) for first time. The specific activity was 6000 U/mg, which is highest in Streptomyces aminopeptidases. Its optimal conditions were 60 °C and pH 8.0, respectively. ScAP exhibited excellent thermal and alkaline pH stability, retained 80.0% maximal activity at 50 °C for 200 h or at pH 9.0 for 24 h. Its activity observed to be complete inhibited by 0.1 mM EDTA and enhanced by Ca2+ and Co2+ to 115.4% and 104.0% respectively. ScAP also has exhibited high specificity towards rice protein on preparation of small peptides. The yield of small rice peptides achieved 66.5%, which is highest by far. Besides, ScAP have significant debittering effect on rice peptides. Results showed that bitter intensity score decreased by 49.0% with optimum condition (0.048% ScAP at 50 °C for 6 h). Therefore, ScAP as dual functional aminopeptidase of hydrolytic and debittering might have a potential application in the production of high yield and low bitterness of small rice peptides.