The Michaelis constants ratio for two substrates with a series of fungal (mould and yeast) β-galactosidases

Within the framework of classical Michaelis-Menten kinetics and in accordance with the customary use of KM for a comparison of enzyme-substrate affinity, the MCR parameter may be interpreted as a relative substrate affinity. This proportion remains nearly the same for different mould (or yeast) β-galactosidases, though the affinity to a particular substrate may vary essentially from enzyme to enzyme. The constancy of MCR may be a manifestation of structural similarity of binding sites for these enzymes.