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)