Asymmetric biosynthesis of L-phosphinothricin by a novel transaminase from Pseudomonas fluorescens ZJB09-108.

• A transaminase from P. fluorescens (Pf -TA) has been identified and expressed. • Pf -TA shows good temperature and pH stability. • Pf -TA catalyzes the synthesis of L-phosphinotricin from PPO using E. coli whole cells. • Up to 500 mM PPO can be used with L-alanine as amine donor. • 75% isolated yield of L-PPT with 99.9% ee was achieved. L-Phosphinotricin (L-PPT) is an active compound of a broad-spectrum herbicide used worldwide. Asymmetric synthesis of L-PPT from 4-(hydroxy(methyl)phosphoryl)-2-oxobutanoic acid (PPO) using transaminase is of great significance due to the 100% theoretical yield and high enantioselectivity. In this study, a new transaminase from Pseudomonas fluorescens ZJB09-108 (named as Pf -TA) was cloned and expressed in E. coli BL21 (DE3). The amino acid sequence analysis showed that the maximum sequence identity of Pf -TA with other transaminases is 74%. This recombinant Pf -TA exhibited a good temperature stability and pH stability. The K m and k cat of Pf -TA toward PPO were 34.02 mmol L−1 and 11.3 s−1, respectively. After optimization of the L-PPT biosynthesis catalyzed by whole-cells of E. coli harboring transaminase, >99% yield of L-PPT with 99.9% of enantiomeric excess was attained at a PPO concentration of 100 mM. High yield of L-PPT (79%) with 99.9% enantiomeric excess was achieved at high PPO concentration of 500 mM as well. These results suggested the recombinant transaminase is a potential candidate for the biosynthesis of L-PPT from PPO. [ABSTRACT FROM AUTHOR]