106 



1. MALONATE 



Table 1-19 



Distribution of Radioactivity Following 3-Hr Incubation of Potato Tuber 

 Slices with Glucose-u-C^* "■ 



" Fresh slices of potato tubers incubated at 28° and pH 5 for 3 hrs with uniformly 

 labeled glucose, in the absence of and presence of 50 xnM malonate. (From Romberger 

 and Norton, 1961.) 



ways for the formation of citrate are known, e.g., the citrase reaction from 

 acetate and oxalacetate, or through isocitrate by the isocitrase reaction 

 from succinate and glyoxylate. However, the free energy changes for these 

 reactions are such that citrate would not accumulate in significant amounts 

 even though the substrates for its formation accumulated. Also the results in 

 Table 1-22 show that the effect is not specific for malonate, but is seen with 

 succinate, malate, fumarate, and other organic anions. The marked effect 

 of glutarate, which is a poor inhibitor of succinate oxidase, suggests that 

 the citrate accumulation may not be related to the block of this enzyme. 

 It may be noted that part of the augmented citrate excretion may be attri- 



