Polyphosphate/ATP-dependent NAD kinase of Corynebacterium glutamicum: Biochemical properties and impact of ppnK overexpression on lysine production
Institute of Molecular Microbiology and Biotechnology, Westfalian Wilhelms University Muenster, 48149, Muenster, Germany. Applied Microbiology and Biotechnology
(Impact Factor: 3.34).
02/2010; 87(2):583-93. DOI: 10.1007/s00253-010-2481-y
Nicotinamide adenine dinucleotide phosphate (NADP) is synthesized by phosphorylation of either oxidized or reduced nicotinamide adenine dinucleotide (NAD/NADH). Here, the cg1601/ppnK gene product from Corynebacterium glutamicum genome was purified from recombinant Escherichia coli and enzymatic characterization revealed its activity as a polyphosphate (PolyP)/ATP-dependent NAD kinase (PPNK). PPNK from C. glutamicum was shown to be active as homotetramer accepting PolyP, ATP, and even ADP for phosphorylation of NAD. The catalytic efficiency with ATP as phosphate donor for phosphorylation of NAD was higher than with PolyP. With respect to the chain length of PolyP, PPNK was active with short-chain PolyPs. PPNK activity was independent of bivalent cations when using ATP, but was enhanced by manganese and in particular by magnesium ions. When using PolyP, PPNK required bivalent cations, preferably manganese ions, for activity. PPNK was inhibited by NADP and NADH at concentrations below millimolar. Overexpression of ppnK in C.
glutamicum wild type slightly reduced growth and ppnK overexpression in the lysine producing strain DM1729 resulted in a lysine product yield on glucose of 0.136 ± 0.006 mol lysine (mol glucose)−1, which was 12% higher than that of the empty vector control strain.
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- "As reported, the impact of ppnK overexpression on lysine production was positive in C. glutamicum, so was isoleucine production in C. glutamicumand thymidine production in E. coli. In this study, we found that PHB accumulated in recombinant C. crenatum P1 and that l-arginine production increased by 20.6 % due to the accumulation of PHB (Fig. 5). "
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- "Overexpression of nadk in E. coli increases the NADPH/NADP ratio, thereby enhancing thymidine biosynthesis . In C. glutamicum, overexpressing the NAD kinase gene improves L-lysine  and L-ornithine  production. Simultaneous chromosomal overexpression of transhydrogenase (pntAB) and NAD kinase (yfjB) genes in E. coli increases the NADPH supply and improves anaerobic isobutanol production . "
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ABSTRACT: Shikimic acid (SA) produced from the seeds of Chinese star anise (Illicium verum) is a key intermediate for the synthesis of neuraminidase inhibitors such as oseltamivir (Tamiflu(R)), an anti-influenza drug. However, plants cannot deliver a stable supply of SA. To avoid the resulting shortages and price fluctuations, a stable source of affordable SA is required. Although recent achievements in metabolic engineering of Escherichia coli strains have significantly increased SA productivity, commonly-used plasmid-based expression systems are prone to genetic instability and require constant selective pressure to ensure plasmid maintenance. Cofactors also play an important role in the biosynthesis of different fermentation products. In this study, we first constructed an E. coli SA production strain that carries no plasmid or antibiotic marker. We then investigated the effect of endogenous NADPH availability on SA production.
The pps and csrB genes were first overexpressed by replacing their native promoter and integrating an additional copy of the genes in a double gene knockout (aroK and aroL) of E. coli. The aroGfbr, aroB, aroE and tktA gene cluster was integrated into the above E. coli chromosome by direct transformation. The gene copy number was then evolved to the desired value by triclosan induction. The resulting strain, E. coli SA110, produced 8.9-fold more SA than did the parental strain E. coli (DeltaaroKDeltaaroL). Following qRT-PCR analysis, another copy of the tktA gene under the control of the 5Ptac promoter was inserted into the chromosome of E. coli SA110 to obtain the more productive strain E. coli SA110. Next, the NADPH availability was increased by overexpressing the pntAB or nadK genes, which further enhanced SA production. The final strain, E. coli SA116, produced 3.12 g/L of SA with a yield on glucose substrate of 0.33 mol/mol.
An SA-producing E. coli strain that carries neither a plasmid nor an antibiotic marker was constructed by triclosan-induced chromosomal evolution. We present the first demonstration that increasing NADPH availability by overexpressing the pntAB or nadK genes significantly enhances SA production.
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- "Our results demonstrated that the increased level of ppnK transcript indeed enhanced the abundance of NADPH in the evolved strain C. glutamicum ΔAPE6937R42 (Figure 3 and Table 2). Lindner et al. reported that over-expression of ppnk improved L-lysine production in C. glutamicum by 12% . Overexpression of nadk, which encodes NAD kinase, increased the NADPH/NADP ratio, which in turn enhanced thymidine biosynthesis in E. coli. "
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L-ornithine is effective in the treatment of liver diseases and helps strengthen the heart. The commercial applications mean that efficient biotechnological production of L-ornithine has become increasingly necessary. Adaptive evolution strategies have been proven a feasible and efficient technique to achieve improved cellular properties without requiring metabolic or regulatory details of the strain. The evolved strains can be further optimised by metabolic engineering. Thus, metabolic evolution strategy was used for engineering Corynebacterium glutamicum to enhance L-ornithine production.
A C. glutamicum strain was engineered by using a combination of gene deletions and adaptive evolution with 70 passages of growth-based selection. The metabolically evolved C. glutamicum strain, named ΔAPE6937R42, produced 24.1 g/L of L-ornithine in a 5-L bioreactor. The mechanism used by C. glutamicum ΔAPE6937R42 to produce L-ornithine was investigated by analysing transcriptional levels of select genes and NADPH contents. The upregulation of the transcription levels of genes involved in the upstream pathway of glutamate biosynthesis and the elevated NADPH concentration caused by the upregulation of the transcriptional level of the ppnK gene promoted L-ornithine production in C. glutamicum ΔAPE6937R42.
The availability of NADPH plays an important role in L-ornithine production in C. glutamicum. Our results demonstrated that the combination of growth-coupled evolution with analysis of transcript abundances provides a strategy to engineer microbial strains for improving production of target compounds.
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