title: [Overexpression of Corynebacterium glutamicum NAD kinase improves L-isoleucine biosynthesis].
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.
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, Jiangsu, China.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Huan
authors.forename: Kun
authors.initials: K
authors.lastname: Li
authors.forename: Feng
authors.initials: F
authors.lastname: Shi
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Wang
mesh_terms: D001951:Brevibacterium / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D048230:Corynebacterium glutamicum / Q000201:enzymology*; D007532:Isoleucine / Q000096:biosynthesis*; D060847:Metabolic Engineering; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D007532:Isoleucine; D009243:NAD; D009249:NADP; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase