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Background  Pyruvate kinase (Pyk) catalyzes the generation of pyruvate and ATP in glycolysis and functions as a key switch in the regulation of carbon flux distribution. Both the substrates and products of Pyk are involved in the tricarboxylic acid cycle, anaplerosis and energy anabolism, which places Pyk at a primary metabolic intersection. Pyks are highly conserved in most bacteria and lower eukaryotes.  Corynebacterium glutamicum  is an industrial workhorse for the production of various amino acids and organic acids. Although  C. glutamicum  was assumed to possess only one Pyk ( pyk1 , NCgl2008), NCgl2809 was annotated as a pyruvate kinase with an unknown role.    Results  Here, we identified that NCgl2809 was a novel pyruvate kinase ( pyk2 ) in  C. glutamicum . Complementation of the WTΔ pyk1 Δ pyk2  strain with the  pyk2  gene restored its growth on  d -ribose, which demonstrated that Pyk2 could substitute for Pyk1  in vivo . Pyk2 was co-dependent on Mn 2+  and K +  and had a higher affinity for ADP than phosphoenolpyruvate (PEP). The catalytic activity of Pyk2 was allosterically regulated by fructose 1,6-bisphosphate (FBP) activation and ATP inhibition. Furthermore,  pyk2  and  ldhA , which encodes  l -lactate dehydrogenase, were co - transcribed as a bicistronic mRNA under aerobic conditions and  pyk2  deficiency had a slight effect on the intracellular activity of Pyk. However, the mRNA level of  pyk2  in the wild-type strain under oxygen deprivation was 14.24-fold higher than that under aerobic conditions. Under oxygen deprivation,  pyk1  or  pyk2  deficiency decreased the generation of lactic acid, and the overexpression of either  pyk1  or  pyk2  increased the production of lactic acid as the activity of Pyk increased. Fed-batch fermentation of the  pyk2 -overexpressing WTΔ pyk1  strain produced 60.27 ± 1.40 g/L of lactic acid, which was a 47% increase compared to the parent strain under oxygen deprivation.    Conclusions  Pyk 2  functioned as a pyruvate kinase and contributed to the increased level of Pyk activity under oxygen deprivation.    Electronic supplementary material  The online version of this article (doi:10.1186/s12896-016-0313-6) contains supplementary material, which is available to authorized users.

A novel pyruvate kinase and its application in lactic acid production under oxygen deprivation in Corynebacterium glutamicum