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BIOLOGICAL SCIENCES / BIOCHEMISTRY
Biosynthesis of the enediyne antitumor antibiotic C-1027 involves a new branching point in chorismate metabolism

Steven G. Van Lanen^*, Shuangjun Lin^*, and Ben Shen^*,,,

*Division of Pharmaceutical Sciences, University of Wisconsin National Cooperative Drug Discovery Group, and Department of Chemistry, University of Wisconsin, Madison, WI 53705

Edited by Christopher T. Walsh, Harvard Medical School, Boston, MA, and approved November 27, 2007 (received for review September 14, 2007)

C-1027 is an enediyne antitumor antibiotic composed of four distinct moieties: an enediyne core, a deoxy aminosugar, a β-amino acid, and a benzoxazolinate moiety. We now show that the benzoxazolinate moiety is derived from chorismate by the sequential action of two enzymes—SgcD, a 2-amino-2-deoxyisochorismate (ADIC) synthase and SgcG, an iron–sulfur, FMN-dependent ADIC dehydrogenase—to generate 3-enolpyruvoylanthranilate (OPA), a new intermediate in chorismate metabolism. The functional elucidation and catalytic properties of each enzyme are described, including spectroscopic characterization of the products and the development of a fluorescence-based assay for kinetic analysis. SgcD joins isochorismate (IC) synthase and 4-amino-4-deoxychorismate (ADC) synthase as anthranilate synthase component I (ASI) homologues that are devoid of pyruvate lyase activity inherent in ASI; yet, in contrast to IC and ADC synthase, SgcD has retained the ability to aminate chorismate identically to that observed for ASI. The net conversion of chorismate to OPA by the tandem action of SgcD and SgcG unambiguously establishes a new branching point in chorismate metabolism.

2-amino-2-deoxyisochorismate dehydrogenase | 2-amino-2-deoxyisochorismate synthase | 3-enolpyruvoylanthranilate

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/cgi/content/full/0708750105/DC1.

To whom correspondence should be addressed. E-mail: bshen{at}pharmacy.wisc.edu

© 2008 by The National Academy of Sciences of the USA

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