Entry of phosphate into yeast cell

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Abstract
Phosphate uptake by Saccharomyces cerevisiae was measured under aerobic conditions. Effects of various substrates and respiratory chain and glycolytic inhibitors were examined. Kinetic analyses of the results indicate 3 components of phosphate uptake. One is associated with oxidative phosphorylation coupled to cytochrome b of the respiratory chain and is effective only under aerobic conditions. The other 2 reactions, which constitute the main cause of phosphate uptake at concentrations above 10-5 [image], are effective under both aerobic and anaerobic conditions. Action of inhibitors indicates that they are both associated with oxidative phosphorylation coupled to the action of glyceraldehyde-3-phosphate dehydrogenase. The rate of 1 of the 2 reactions is interpreted as being limited by the phosphorylation of adenosine diphosphate. The rate of the other reaction, which is predominant at high phosphate concentrations (> 10-3 [image]) and optimal glucose concentrations (0.3 M), appears to be limited by the action of hexokinase.