Glycolysis performs ten stepwise chemical transformations and at the third step of glycolysis, major checkpoint exists, regulated by the enzyme phosphofructokinase (PFK). The PFK enzyme being an integral part of a primeval but universal pathway may be regarded as an excellent marker in determining the proximity among the different bacterial species at the metabolic level. In this study an attempt was made to capture the extent of compositional variability that has been accommodated by the PFK enzyme sequence, yet keeping its primary functional attribute intact. In this study more than eight thousand PFK amino acid sequences belonging to 782 bacterial genera comprising the entire eubacterial domain were comprehensively analyzed. The variability in the amino acid usage pattern existing within the PFK enzyme was found to be astonishing, and resolutely reflected in the GRAVY as well as the pI values. Barring a few amino acids such as histidine, cysteine and tryptophan, which are in general less frequent, nearly all the other amino acids showed a significant fluctuation within the compositional profile of PFK. Even at the generic level substantial compositional variability was detected from this analysis. Mycoplasma and Acinetobacter species were found to be extremely opposite in nature considering their PFK compositional profile.
