Structure and substrate specificity determinants of the taurine biosynthetic enzyme cysteine sulphinic acid decarboxylase

MpADC, an L-aspartate-α-decarboxylase, from Myzus persicae, that enables production of β-alanine with high yield by whole-cell enzymatic catalysis

BACKGROUND

β-Alanine is a precursor of many important pharmaceutical products and food additives, its market demand is continuously increasing nowadays. Whole-cell catalysis relying on the recombinant expression of key β-alanine synthesizing enzymes is an important method to produce β-alanine. Nevertheless, β-alanine synthesizing enzymes found so far have problems including easy inactivation, low expression or poor catalytic activity, and it remains necessary to develop new enzymes.

RESULTS

Herein, we characterized an L-aspartate-α-decarboxylase, MpADC, from an aphid, Myzus persicae. It showed excellent catalytic activity at pH 6.0-7.5 and 37 °C. With the help of chaperone co-expression and N-terminal engineering guided by AlphaFold2 structure prediction, the expression and catalytic ability of MpADC in Escherichia coli were significantly improved. Using 50 g/L of E. coli cells expressing the MpADC-∆39 variant cultured in a 15-L fermenter, 232.36 g/L of β-alanine was synthesized in 13.5 h, with the average β-alanine yield of 17.22 g/L/h, which is best known so far.

CONCLUSIONS

Our research should facilitate the production of β-alanine in an environment-friendly manner.

CSAD Ameliorates Lipid Accumulation in High-Fat Diet-Fed Mice

Non-alcoholic fatty liver disease (NAFLD) is a chronic metabolic disease manifested in hepatic steatosis, inflammation, fibrosis, etc., which affects over one-quarter of the population around the world. Since no effective therapeutic drugs are available to cope with this widespread epidemic, the functional research of genes with altered expression during NAFLD helps understand the pathogenesis of this disease and the development of new potential therapeutic targets for drugs. In the current work, we discovered via the analysis of the Gene Expression Omnibus (GEO) dataset that cysteine sulfinic acid decarboxylase (CSAD) decreased significantly in NAFLD patients, which was also confirmed in multiple NAFLD mouse models (HFD-fed C57BL/6J, db/db and HFHFrHC-fed C57BL/6J mice). Next, CSAD's function in the progression of NAFLD was explored using AAV-mediated liver-directed gene overexpression in an HFD-fed mouse model, where the overexpression of CSAD in the liver could alleviate NAFLD-associated pathologies, including body weight, liver/body weight ratio, hepatic triglyceride and total cholesterol, and the degree of steatosis. Mechanically, we found that the overexpression of CSAD could increase the expression of some genes related to fatty acid β-oxidation (Acad1, Ppara, and Acox1). Furthermore, we also detected that CSAD could improve mitochondrial injury in vitro and in vivo. Finally, we proposed that the effect of CSAD on lipid accumulation might be independent of the taurine pathway. In conclusion, we demonstrated that CSAD is involved in the development of NAFLD as a protective factor, which suggested that CSAD has the potential to become a new target for drug discovery in NAFLD.