High-level production of valine by expression of the feedback inhibition-insensitive acetohydroxyacid synthase in Saccharomyces cerevisiae

Metabolic Engineering
Natthaporn TakphoHiroshi Takagi

Abstract

Valine, which is one of the branched-chain amino acids (BCAAs) essential for humans, is widely used in animal feed, dietary supplements and pharmaceuticals. At the commercial level, valine is usually produced by bacterial fermentation from glucose. However, valine biosynthesis can also proceed in the yeast Saccharomyces cerevisiae, which is a useful microorganism in fermentation industry. In S. cerevisiae, valine biosynthesis is regulated by valine itself via the feedback inhibition of acetohydroxyacid synthase (AHAS), which consists of two subunits, the catalytic subunit Ilv2 and the regulatory subunit Ilv6. In this study, to improve the valine productivity of yeast cells, we constructed several variants of Ilv6 by introducing amino acid substitutions based on a protein sequence comparison with the AHAS regulatory subunit of E. coli. Among them, we found that the Asn86Ala, Gly89Asp and Asn104Ala variants resulted in approximately 4-fold higher intracellular valine contents compared with those in cells with the wild-type Ilv6. The computational analysis of Ilv6 predicted that Asn86, Gly89 and Asn104 are located in the vicinity of a valine-binding site, suggesting that amino acid substitutions at these positions induce conformat...Continue Reading

Citations

Mar 15, 2020·Biotechnology Journal·Melanie MindtVolker F Wendisch
Nov 21, 2019·Applied Microbiology and Biotechnology·Yangyang ZhanShouwen Chen
Nov 22, 2018·Frontiers in Microbiology·Akaraphol WatcharawipasHiroshi Takagi
Dec 6, 2020·Journal of Bioscience and Bioengineering·Asuka MizobataHiroyasu Ogino
Sep 1, 2021·Microbial Cell Factories·Hui GaoZhiming Rao

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