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Abstract
[U-14C]-D-Glucose (1 and 20 mm) was added to glucose-grown suspension cultures of Puccinia graminis, and the sequence of movement of the label into metabolic intermediates was determined under steady-state conditions. Radioactive label moved most rapidly into cellular pools of free glucose, amino acids and phosphate esters of trehalose and glucose, and less rapidly into free fructose. No lag was detected in the movement of label into any of these compounds. Thus fructose was the first free carbohydrate synthesized from glucose. Radioactive label moved more slowly, and with an initial lag phase, into trehalose, glucitol and mannitol; the lag was more pronounced for mannitol than glucitol. Kinetic data and specific activity measurements to identify precursors suggest that trehalose was formed via trehalose phosphate, mannitol via fructose, and glucitol via both glucose and fructose. Steady-state specific activities of all free intracellular carbohydrates were much lower (15-50%) than that of the exogenous glucose, indicating that unlabelled carbon was entering these pools from storage reserves or other components from the culture medium.
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