Determination of D-Isocitrate

D-isocitrate is an intermediate product of the citrate cycle. It is formed as a by-product of the fermentative production of citric acid. The enzymatic assay of isocitrate is based on the oxidative decarboxylation to a-ketoglutarate in the presence of isocitrate dehydrogenase (EC 1.1.1.42)  

The reaction has been coupled to the electrochemical detection of the liberated NADPH at a chemically modified carbon electrode (Nakamura 

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Fluorimetric methods involving six dehydrogenases have been used to determine the concentrations of 21 of the more common organic acids (58). Sensitivity of the methods range from 0.02 fxg/m for determination of D-isocitric acid with isocitrate dehydrogenase to 200 /xg/ml for determination of D-tartaric acid with malate dehydrogenase. 

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