Transport of riboflavin into yeast cells.

摘要: Riboflavin-requiring mutants of Saccharomyces cerevisiae are able to transport 14C-labeled riboflavin into the cell, although no significant is seen in commercial yeast or parent strain from which were derived. Transport activity greatest early mid-log phase anaerobic growth and declines sharply late log phase. In aerobically grown cells substantially lower at all stages growth. assay devised for its measurement, shows a sharp pH optimum 7.5, strong temperature dependence (EA = 23,100 cal/mol), saturation kinetics with respect (Km 15 muM), characteristics consistent carrier-mediated mechanism. Monovalent inorganic cations, particularly K+ Rb+, stimulate uptake, while certain organic cations inhibitory. Besides only 7-methylriboflavin, 8-methylriboflavin, 5-deazaflavin have been found serve as substrates, lumiflavin, tetraacetylriboflavin, N10-[4'-carboxybutyl]-7,8-dimethylisoalloxazine do not, number flavin analogs ribityl side chain modified good competitive inhibitors uptake. Compounds resembling chain, such sugars sugar alcohols, not inhibit. An apparent inhibition uptake by D-glucose, D-mannose, D-fructose, develops course assay, proved result stimulation an opposing process, release cells.