Citric acid accumulation and the absence of a-ketoglutaric acid in most samples
(Figs. 6–11) may be related to aconitase and isocitrate dehydrogenase enzymes been affected. Conversely, the presence of a-ketoglutaric acid may be attributed to transamination reactions between oxaloacetate and glutamate mediated by aspartate aminotransferase to produce aspartate and aketoglutarate, or alternatively, to direct synthesis since most mitochondria contain glutamate dehydrogenase. This enzyme is able to oxidize glutamate to a-ketoglutarate to produce NADHand ammonia. Aspartate may
also be involved in purine synthesis in a more complex
reaction scheme that can release fumarate, which in turn may enter the mitochondria (Day & Copeland, 1993)