Active Transport of l-Valine by Streptococcus Diacetilactis

Transport of L-valine by resting cells (16 hr) of Streptococcus diacetilactisstrain 18-16 was sensitive to changes in temperature resulting in a temperature coefficient of about 1.8.Moreover, the system was activated by glucose and inhibited by both azide and 2,4-dinitrophenol, indicating the probable involvement of metabolically produced energy.Lipoic acid (oxidized) and pyridoxal phosphate both increased the rate of n-valine uptake and when added together they exerted a synergistic effect.Rate of transport was influenced by the external amino acid and peptide concentrations in the suspending media.Studies at various pH levels revealed the possible presence of two separate uptake systems for L-valine in intact cells of this organism.