Biosynthesis of aflatoxins

Abstract

The role of zinc on the primary metabolism of Aspergillus parasiticus in relation to aflatoxin biosynthesis was studied. Zinc deficiency impaired growth and metabolism of nucleic acid and protein while stimulating that of lipid. The activities of enzymes of glycolytic cycle were affected indicating that these are zinc dependent enzymes. Impaired glycolytic cycle tends to reduce the level of primary metabolites like pyruvate, citrate and oxaloacetate which trigger aflatoxin formation. During stationary phase these precursors accumulate as these are not used up for the synthesis of secondary metabolites (aflatoxins) due to zinc deficiency. ATP and energy-charge (E.C.) which are important for various physiological processes like growth are reduced in zinc deficiency. Also zinc deficiency results in low levels of AMP which favour synthesis of lipid. Inorganic phosphate accumulated due to zinc deficiency and this may be unfavourable for aflatoxin synthesis.