Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2004
Publication Date: 6/30/2004
Citation: Chang, P.-K., Yabe, K., Yu, J. 2004. Conversion of versiconal hemiacetal acetate to versiconal and versiconol acetate to versiconol by Aspergillus parasiticus estA-encoded esterase during aflatoxin biosynthesis [abstract]. Annual Meeting of American Society for Microbiology, New Orleans, Louisiana. Interpretive Summary:
Technical Abstract: In aflatoxin biosynthesis, the pathway for the conversion of 1-hydroxyversicolorone to versiconal hemiacetal acetate (VHA) to versiconal (VHOH) involves two metabolic grids. In the grids, the steps from VHA to VHOH and versiconol acetate (VOAc) to versiconol (VOH) had been proposed to be catalyzed by the same esterase. We deleted the estA gene in the aflatoxin gene cluster of A. parasiticus SRRC 2043, an O-methylstergimatocystin (OMST)-accumulating strain. The estA-deleted mutants mainly accumulated HVA and versicolorin A (VA), a small amount of VOAc, and other downstream aflatoxin intermediates, including VHOH, versicolorin B and OMST. In contrast, a VA-accumulating mutant, NIAH-9, acumulated VA exclusively, and neither VHA nor VOAc were produced. Addition of dichlorvos to the transformation recipient RHN1, an estA-deleted mutant, and NIAH-9 caused accumulation of only VHA and VOAc. Furthermore, in vitro enzyme assays showed that the esterase activities catalyzing VHA to VHOH in the cell-free extracts of two estA-deleted mutants were decreased to approximately 10 percent that of RHN1. Similar decreases in the esterase activities catalyzing VOAc to VOH were obtained for the estA-deleted mutants when compared to RHN1. These results demonstrate that the estA-encoded esterase catalyzes primarily both the conversion to VHA to VHOH and VOAc to VOH during aflatoxin biosynthesis.