ABSTRACT
In this chapter, the authors discuss their findings that is concerned with the catalytic and regulatory properties of the mannitol Enzyme II of the E. coli phosphotransferase system (PTS). The sugar is transported across the membrane and concomitantly phosphorylated by a PTS–mediated mechanism. In this process the phosphoryl group of phosphoenolpyruvate is transferred sequentially from phosphoenolpyruvate to Enzyme I and HPr, the two energy coupling proteins of the phosphotransferase system. The Enzyme II also catalyzes both unidirectional and bidirectional exchange translocation of its sugar substrate. The mannitol Enzyme II may effect dephosphorylation of this regulatory protein. The regulatory proteins for the hexitol operons might exhibit common structural features and might even substitute for one another under appropriate conditions. The mutants isolated for their ability to grow on citrate plus fructose or citrate plus mannitol were frequently defective for the fructose or mannitol Enzyme II. The results reports emphasize the multifunctional nature of the protein both in catalysis and regulation.
