Binding of the substrate analog perseitol to phosphorylated and unphosphorylated enzyme IImtl of the phosphoenolpyruvate-dependent phosphotransferase system of Escherichia coli

• Published in: Biochemistry (Easton) 1993-06, Vol.32 (22), p.5848-5854
• Main Authors: Lolkema, Juke S, Wartna, Ellen S, Robillard, George T
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Binding, Competitive; Biological and medical sciences; Escherichia coli - drug effects; Escherichia coli - enzymology; Escherichia coli Proteins; Fundamental and applied biological sciences. Psychology; Heptoses - metabolism; Heptoses - pharmacology; Kinetics; Mannitol - metabolism; Miscellaneous; Monosaccharide Transport Proteins; Phosphoenolpyruvate Sugar Phosphotransferase System - antagonists & inhibitors; Phosphoenolpyruvate Sugar Phosphotransferase System - metabolism; Phosphorylation; Proteins
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00073a018

Enzyme IImtl catalyzes the concomitant transport and phosphorylation of the hexitol mannitol. Here we demonstrate that the heptitol perseitol 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 perseitol were inferred from the inhibition by perseitol of mannitol phosphorylation and uptake. Apparent affinities of the unphosphorylated enzyme follow from the inhibition of mannitol binding to the enzyme. Mechanistic interpretations of the apparent inhibition constants are discussed, and it is concluded that phosphorylation of the cytoplasmic domain of enzyme IImtl has little effect on the affinity of the membrane-bound domain of the enzyme for perseitol.