Simultaneously Enhancing the Stability and Catalytic Activity of Multimeric Lysine Decarboxylase CadA by Engineering Interface Regions for Enzymatic Production of Cadaverine at High Concentration of Lysine

摘要

> Cadaverine (1,5‐diaminopentane) is a major source of many industrial polyamides such as nylon and chelating agents. Currently, cadaverine is produced by the microbial fermentation of glucose to lysine, which is then decarboxylated by lysine decarboxylase (CadA). However, utilizing CadA for cadaverine production causes enzyme instability. In order to stabilize the CadA homo‐decamer structure for in vitro decarboxylation reaction, mutants are designed. Of the four disulfide bond mutants in the multimeric interfacial region, B1 (F14C/K44C) showed a 216‐folds increase in the half‐life of CadA at 60?°C. On top of B1, another round of mutant screening is performed around F14C and K44C to generate B1/L7M/N8G, which is then examined for cadaverine production (2M lysine and 10% v/v of cell‐extract at 50?°C). The reaction pH increased from 4.9 to 8.3, and the final titer of the mutant is 157?g?L ?1 , that is, 76.7% conversion yield in 9.5?h, whereas the wild‐type gave 119?g?L ?1 , that is, 58.2% conversion yield in 9.5?h.