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Applied and Environmental Microbiology, June 2004, p. 3593-3599, Vol. 70, No. 6
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.6.3593-3599.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

The Aspergillus parasiticus estA-Encoded Esterase Converts Versiconal Hemiacetal Acetate to Versiconal and Versiconol Acetate to Versiconol in Aflatoxin Biosynthesis

Perng-Kuang Chang,1*,{dagger} Kimiko Yabe,2,{dagger} and Jiujiang Yu1

Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, Louisiana 70124,1 National Food Research Institute, Tsukuba, Ibaraki 305-8642, Japan2

Received 28 July 2003/ Accepted 2 March 2004

In aflatoxin biosynthesis, the pathway for the conversion of 1-hydroxyversicolorone to versiconal hemiacetal acetate (VHA) to versiconal (VHOH) is part of a metabolic grid. In the grid, the steps from VHA to VHOH and from versiconol acetate (VOAc) to versiconol (VOH) may be catalyzed by the same esterase. Several esterase activities are associated with the conversion of VHA to VHOH, but only one esterase gene (estA) is present in the complete aflatoxin gene cluster of Aspergillus parasiticus. We deleted the estA gene from A. parasiticus SRRC 2043, an O-methylsterigmatocystin (OMST)-accumulating strain. The estA-deleted mutants were pigmented and accumulated mainly VHA and versicolorin A (VA). A small amount of VOAc and other downstream aflatoxin intermediates, including VHOH, versicolorin B, and OMST, also were accumulated. In contrast, a VA-accumulating mutant, NIAH-9, accumulated VA exclusively and neither VHA nor VOAc were produced. Addition of the esterase inhibitor dichlorvos (dimethyl 2,2-dichlorovinylphosphate) to the transformation recipient strain RHN1, an estA-deleted mutant, or NIAH-9 resulted in the accumulation of only VHA and VOAc. In in vitro enzyme assays, the levels of the esterase activities catalyzing the conversion of VHA to VHOH in the cell extracts of two estA-deleted mutants were decreased to approximately 10% of that seen with RHN1. Similar decreases in the esterase activities catalyzing the conversion of VOAc to VOH were also obtained. Thus, the estA-encoded esterase catalyzes the conversion of both VHA to VHOH and VOAc to VOH during aflatoxin biosynthesis.

* Corresponding author. Mailing address: Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 1100 Robert E. Lee Blvd., New Orleans, LA 70124. Phone: (504) 286-4208. Fax: (504) 286-4419. E-mail: pkchang{at}srrc.ars.usda.gov.

{dagger} P.-K.C. and K.Y. contributed equally to this work.

Applied and Environmental Microbiology, June 2004, p. 3593-3599, Vol. 70, No. 6
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.6.3593-3599.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



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  • Sakuno, E., Wen, Y., Hatabayashi, H., Arai, H., Aoki, C., Yabe, K., Nakajima, H. (2005). Aspergillus parasiticus Cyclase Catalyzes Two Dehydration Steps in Aflatoxin Biosynthesis. Appl. Environ. Microbiol. 71: 2999-3006 [Abstract] [Full Text]  


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