Phosphofructokinases from Lactobacteriaceae. II. Purification and properties of phosphofructokinase from Streptococcus thermophilus.

Phosphofructokinase (ATP : D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) from Streptococcus thermophilus has been purified. It is a tetramer composed of identical subunits of molecular weight 36 000 and exhibits Michaelis-Menten kinetics. Compared to the phosphofructokinases from taxonomically related bacteria, the enzyme from S. thermophilus is more stable at high temperatures. In addition, it has been demonstrated that the phosphofructokinases from lactobacteria and also from Bacillus stearothermophilus show immunologic cross-reaction. In spite of the significantly different kinetic properties and the different thermostability of these enzymes, this finding indicates great structural resemblance.