Abstract
Experiments were carried out to investigate the effects of various factors on the activity and conformation of recombinant leucine aminopeptidase of Bacillus kaustophilus CCRC 11223 (BkLAP) and potential utilization of BkLAP in the hydrolysis of anchovy protein. Optimal temperature and pH of BkLAP were 70 °C and 8.0 in potassium-phosphate buffer, respectively, and the activity was strongly stimulated by Ni2+, followed by Mn2+ and Co2+. Conformational studies via circular dichroism spectroscopy indicated that various factors could influence the secondary structure of BkLAP to different extents and further induce the changes in enzymatic activity. The secondary structure of BkLAP was slightly modified by Ni2+ at the concentration of 1×10−4 M, however, significant changes on the secondary structures of the enzyme were observed when Hg2+ was added to the concentration of 1×10−4 M. The potential application of BkLAP was evaluated through combination with the commercial or endogenous enzyme to hydrolysis the anchovy protein. Results showed that combining the BkLAP with other enzymes could significantly increase the degree of hydrolysis and amino acid component of hydrolysate. In this regard, BkLAP is a potential enzyme that can be used in the protein hydrolysate industry.
Highlights
Every year, industrial processing of feeds destined for human nutrition and animal consumption results in high amounts of agroindustrial residues
Proteins could be modified by treatment with proteolytic enzymes, the functional properties and nutrition value of proteins could be improved by enzymatic hydrolysis [6], which can generate polypeptides and free amino acids [7,8]
To obtain the optimal conditions for the production of active Bacillus kaustophilus leucine aminopeptidase (BkLAP), many efforts have been made in heterogeneous gene expression of BkLAP in E. coli BL21, including the IPTG
Summary
Industrial processing of feeds destined for human nutrition and animal consumption results in high amounts of agroindustrial residues. These residues are receiving greater attention in terms of quality control and have been classified as agroindustrial by-products [1]. Aminopeptidases are exopeptidases that selectively release N-terminal amino acid residues from polypeptides and proteins. These enzymes from various sources can be used successfully to debitter protein hydrolyzates. The biological significance and the applied aspect of this enzyme are still not fully understood This topic promoted a number of theoretical studies on the environmental effects of divalent cations, temperature, pH in the activity and structure of the enzyme. The data presented here considerably expand our basic knowledge about this enzyme, and provide the useful information for its application in food processing industry
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