Molecular properties and transcriptional control of the phosphofructokinase and pyruvate kinase genes in a ruminal bacterium, Streptococcus bovis

Molecular properties of pyruvate kinase (PYK) and phosphofructokinase (PFK) in Streptococcus bovis and transcriptional control of the two enzymes were examined. Sequence analysis indicated that the PYK gene (pyk) clusters with the PFK gene (pfk) and several other genes. It was demonstrated that the pyk and pfk are cotranscribed and their transcription appeared to be regulated at the transcriptional level in response to the sugars supplied. The intracellular pyk-mRNA level was lower in a catabolite control protein A (CcpA)-disrupted mutant than in its parent strain, and a binding site of CcpA was found in the upstream region of pfk. These results suggest that pfk-pyk transcription is enhanced by CcpA. A recombinant pyk-overexpressing strain showed approximately five-fold higher PYK activity, but it did not affect the growth rate or formate-to-lactate ratio significantly, suggesting that the flux in the glycolytic pathway is not altered by an increase in PYK activity.