Effect of Zinc on tricarboxylic acid cycle intermediates and enzymes in relation to aflatoxin biosynthesis.

The stimulatory action of zinc on aflatoxin production by Aspergillus parasiticus NRRL3240 has been investigated by studying the levels of tricarboxylic acid (TCA) cycle intermediates and related enzymes in the fungal mycelium. During the stationary phase of growth, the levels of alpha-keto acids declined in zinc-sufficient cultures compared with those in zinc-dificient cultures. TCA cycle enzymes did not show any significant changes due to zinc availability. In zinc-deficient cultures, enzymes of the TCA cycle had maximum activity on the fourth day, after which their activity declined. In zinc-sufficient cultures, some enzymes showed maximum activity on the fourth day, others on the second day.