Overexpression of Corynebacterium glutamicum NAD kinase improves L-isoleucine biosynthesis.
- Author:
Xiaojing HUAN
1
;
Kun LI
;
Feng SHI
;
Xiaoyuan WANG
Author Information
1. State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, Jiangsu, China.
- Publication Type:Journal Article
- MeSH:
Brevibacterium;
genetics;
metabolism;
Cloning, Molecular;
Corynebacterium glutamicum;
enzymology;
Isoleucine;
biosynthesis;
Metabolic Engineering;
NAD;
metabolism;
NADP;
metabolism;
Phosphotransferases (Alcohol Group Acceptor);
genetics;
metabolism;
Recombinant Proteins;
genetics;
metabolism
- From:
Chinese Journal of Biotechnology
2012;28(9):1038-1047
- CountryChina
- Language:Chinese
-
Abstract:
NAD kinase catalyzes the phosphorylation of coenzyme I [NAD(H)] to form coenzyme II [NADP(H)], and NADPH is an important cofactor in L-isoleucine biosynthesis. In order to improve NADPH supply, ppnK, the gene encoding NAD kinase in Corynebacterium glutamicum was cloned and separately expressed in an L-isoleucine synthetic strain, Brevibacterium lactofermentum JHI3-156, by an inducible expression vector pDXW-8 and a constitutive expression vector pDXW-9. Compared with the control strain JHI3-156/pDXW-8, NAD kinase activity of the inducible ppnK-expressing strain JHI3-156/pDXW-8-ppnK was increased by 83.5%. NADP(H)/NAD(H) ratio was also increased by 63.8%. L-isoleucine biosynthesis was improved by 82.9%. Compared with the control strain JHI3-156/pDXW-9, NAD kinase activity of the constitutive ppnK-expressing strain JHI3-156/pDXW-9-ppnK was increased by 220%. NADP(H)/ NAD(H) ratio and NADPH concentration were increased by 134% and 21.7%, respectively. L-isoleucine biosynthesis was increased by 41.7%. These results demonstrate that NAD kinase can improve the coenzyme II supply and L-isoleucine biosynthesis, which would also be useful for biosynthesis of other amino acids.
