BINDING OF THE SUBSTRATE-ANALOG PERSEITOL TO PHOSPHORYLATED AND UNPHOSPHORYLATED ENZYME-IIMTL OF THE PHOSPHOENOLPYRUVATE-DEPENDENT PHOSPHOTRANSFERASE SYSTEM OF ESCHERICHIA-COLI

Enzyme II(mtl) catalyzes the concomitant transport and phosphorylation of the hexitol mannitol. Here we demonstrate that the heptitol persei tol is not phosphorylated and not transported by the enzyme. However, the enzyme binds perseitol with an affinity comparable to the affinity for mannitol. Apparent affinities of the phosphorylated enzyme for pe rseitol were inferred from the inhibition by perseitol of mannitol pho sphorylation and uptake. Apparent affinities of the unphosphorylated e nzyme follow from the inhibition of mannitol binding to the enzyme. Me chanistic interpretations of the apparent inhibition constants are dis cussed, and it is concluded that phosphorylation of the cytoplasmic do main of enzyme II(mtl) has little effect on the affinity of the membra ne-bound domain of the enzyme for perseitol.