Expression of Novel L-Leucine Dehydrogenase and High-Level Production of L-Tert-Leucine Catalyzed by Engineered Escherichia coli

Yuan-Yuan Jia; Yu-Li Xie; Lu-Lu Yang; Hong-Ling Shi; Yun-Feng Lu; Si-Pu Zhang; Cun-Duo Tang; Lun-Guang Yao; Yun-Chao Kan

doi:10.3389/fbioe.2021.655522

Expression of Novel L-Leucine Dehydrogenase and High-Level Production of L-Tert-Leucine Catalyzed by Engineered Escherichia coli

Front Bioeng Biotechnol. 2021 Mar 30:9:655522. doi: 10.3389/fbioe.2021.655522. eCollection 2021.

Authors

Yuan-Yuan Jia^{1

2}, Yu-Li Xie^{1

2}, Lu-Lu Yang^{1

2}, Hong-Ling Shi^{1

2}, Yun-Feng Lu^{1

2}, Si-Pu Zhang³, Cun-Duo Tang^{1

2}, Lun-Guang Yao^{1

2}, Yun-Chao Kan¹

Affiliations

¹ Henan Provincial Engineering Laboratory of Insect Bio-reactor, Henan Key Laboratory of Ecological Security for Water Source Region of Mid-line of South-to-North, Nanyang Normal University, Nanyang, China.
² School of Life Sciences and Agricultural Engineering, Nanyang Normal University, Nanyang, China.
³ Henan Academy of Agricultural Sciences, Zhengzhou, China.

Abstract

Leucine dehydrogenase (LDH) is a NAD⁺-dependent oxidoreductase, which can selectively catalyze α-keto acids to obtain α-amino acids and their derivatives. It plays a key role in the biosynthesis of L-tert-leucine (L-Tle). As a non-naturally chiral amino acid, L-Tle can be used as an animal feed additive, nutrition fortifier, which is a perspective and important building block in the pharmaceutical, cosmetic, and food additive industry. In this study, four hypothetical leucine dehydrogenases were discovered by using genome mining technology, using the highly active leucine dehydrogenase LsLeuDH as a probe. These four leucine dehydrogenases were expressed in Escherichia coli BL21(DE3), respectively, and purified to homogeneity and characterized. Compared with the other enzymes, the specific activity of PfLeuDH also shows stronger advantage. In addition, the highly selective biosynthesis of L-Tle from trimethylpyruvic acid (TMP) was successfully carried out by whole-cell catalysis using engineered E. coli cells as biocatalyst, which can efficiently coexpress leucine dehydrogenase and formate dehydrogenase. One hundred-millimolar TMP was catalyzed for 25 h, and the yield and space-time yield of L-Tle reached 87.38% (e.e. >99.99%) and 10.90 g L^-1 day^-1. In short, this research has initially achieved the biosynthesis of L-Tle, laying a solid foundation for the realization of low-cost and large-scale biosynthesis of L-Tle.

Keywords: biocatalysis; expression; feed additive; formate dehydrogenase; leucine dehydrogenase.