Enhancing the catalytic efficiency of M32 carboxypeptidase by semi-rational design and its applications in food taste improvement.

BACKGROUND: Carboxypeptidase is an exopeptidase that hydrolysis amino acids at the C-terminal end of the peptide chain and has a wide range of applications in food. However, in industrial applications, the relatively low catalytic efficiency of carboxypeptidases is one of the main limiting factors for industrialization.

RESULTS: The study has elevated the catalytic efficiency of Bacillus megaterium M32 carboxypeptidase (BmeCPM32) through semi-rational design. Firstly, the optimal mutant, BmeCPM32-M2, obtained through single-site mutagenesis and combinatorial mutagenesis, specific activity was 2.2-fold higher than that of the wild type (187.9 vs. 417.8 U mg-1 ), and catalytic efficiency was 2.9-fold higher (110.14 vs. 325.75 s-1  mM-1 ). Secondly, compared to the wild type, BmeCPM32-M2 exhibited a 1.8-fold increase in half-life at 60 °C, with no significant changes in its enzymatic properties (optimal pH, optimal temperature). Finally, BmeCPM32-M2 significantly increased the umami intensity of soy protein isolate hydrolysate (SPIA) by 55% and reduced bitterness by 83%, indicating its potential in developing tasty protein components.

CONCLUSION: Our research has revealed that the strategy based on protein sequence evolution and computational residue mutation energy has improved the catalytic efficiency of BmeCPM32. Molecular dynamics simulations have revealed that a smaller substrate binding pocket and increased enzyme-substrate affinity are the reasons for enhancing catalytic efficiency, Furthermore the number of hydrogen bonds and solvent and surface area, which may contribute to the improvement of thermostability. Finally, the de-bittering effect of BmeCPM32-M2 in soy protein isolate hydrolysate suggests its potential in developing palatable protein components. This article is protected by copyright. All rights reserved.