Engineering aminoacyl-tRNA synthetase activity to enhance branched-chain amino acid biosynthesis

Abstract

Branched-chain amino acids (BCAA; valine, leucine, and isoleucine) are high-value metabolites. Its microbial production can be significantly increased by metabolic engineering. While pathway engineering dominates current efforts, the BCAA-specific aminoacyl-tRNA synthetases (aaRS) represent a powerful but overlooked lever. They not only charge tRNAs for accurate translation but also influence cellular BCAA availability. Disrupting aaRS activity or tRNA charging increases (p)ppGpp levels, which activates BCAA biosynthesis by means of the stringent response and attenuation control. Recent research has begun to harness this link by engineering aaRS-tRNA pairs to create growth-coupled selection systems, which have successfully increased amino acid titers in Escherichia coli and Corynebacterium glutamicum. Yet, direct engineering of BCAA aaRS remains rare. Integrating tRNA modifications, targeted aaRS mutagenesis, and synthetic biology tools offers a compelling route to engineer superior microbial cell factories for industrial-scale BCAA production.

Keywords: Amino acid biosynthesis; Amino acids-producing bacteria; Aminoacyl-tRNA synthetases (aaRS); BCAA; Branched-chain amino acid biosynthesis; Metabolic engineering.