Transport of d -Arabinose-5-Phosphate and d -Sedoheptulose-7-Phosphate by the Hexose Phosphate Transport System of Salmonella typhimurium

Abstract

d -Arabinose-5-phosphate and d -sedoheptulose-7-phosphate were found to be substrates, although not inducers, of the hexose phosphate transport system of Salmonella typhimurium . Transport of these two sugar phosphates by wild-type strains required preinduction of the hexose phosphate transport system. A mutant of S. typhimurium constitutive for this system also transported d -arabinose-5-phosphate and d -sedoheptulose-7-phosphate in a constitutive fashion. Glucose-6-phosphate was a potent competitor of the transport of both d -arabinose-5-phosphate and d -sedoheptulose-7-phosphate. The K m values for transport of d -glucose-6-phosphate, d -arabinose-5-phosphate, and d -sedoheptulose-7-phosphate were 0.13, 0.32 and 1.61 mM, respectively. The apparent V max values for transport of d -glucose-6-phosphate, d -arabinose-5-phosphate, and d -sedoheptulose-7-phosphate were 6.3, 13.2 and 3.0 nmol per min per 5 × 10 8 bacteria, respectively. d -Ribulose-5-phosphate and d -xylulose-5-phosphate did not inhibit transport of the above substrates, whereas d -ribose-5-phosphate was a weak inhibitor of d -sedoheptulose-7-phosphate transport.