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Antimicrobial Agents and Chemotherapy, July 2003, p. 2065-2071, Vol. 47, No. 7
0066-4804/03/$08.00+0     DOI: 10.1128/AAC.47.7.2065-2071.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Biosynthetic Origin of Hygromycin A

El-Sayed E. Habib,^1, J. Neel Scarsdale,² and Kevin A. Reynolds^1*

Departments of Medicinal Chemistry,¹ Biochemistry, Virginia Commonwealth University, Richmond, Virginia 23219²

Received 12 February 2003/ Returned for modification 25 March 2003/ Accepted 21 April 2003

Hygromycin A, an antibiotic produced by Streptomyces hygroscopicus, is an inhibitor of bacterial ribosomal peptidyl transferase. The antibiotic binds to the ribosome in a distinct but overlapping manner with other antibiotics and offers a different template for generation of new agents effective against multidrug-resistant pathogens. Reported herein are the results from a series of stable-isotope-incorporation studies demonstrating the biosynthetic origins of the three distinct structural moieties which comprise hygromycin A. Incorporation of [1-¹³C]mannose and intact incorporation of D-[1,2-¹³C₂]glucose into the 6-deoxy-5-keto-D-arabino-hexofuranose moiety are consistent with a pathway in which mannose is converted to an activated L-fucose, via a 4-keto-6-deoxy-D-mannose intermediate, with a subsequent unusual mutation of the pyranose to the corresponding furanose. The aminocyclitol moiety was labeled by D-[1,2-¹³C₂]glucose in a manner consistent with formation of myo-inositol and a subsequent unprecedented oxidation and transamination of the C-2 hydroxyl group to generate neo-inosamine-2. Incorporation of [carboxy-¹³C]-4-hydroxybenzoic acid and intact incorporation of [2,3-¹³C₂]propionate are consistent with a polyketide synthase-type decarboxylation condensation to generate the 3,4-dihydroxy--methylcinnamic acid moiety of hygromycin A. No labeling of hygromycin A was observed when [3-¹³C]tyrosine, [3-¹³C]phenylalanine, or [carboxy-¹³C]benzoic acid was used, suggesting that the 4-hydroxybenzoic acid is derived directly from chorismic acid. Consistent with this hypothesis was the observation that hygromycin A titers could be reduced by addition of N-(phosphonomethyl)-glycine (an inhibitor of chorismic acid biosynthesis) and restored by coaddition of 4-hydroxybenzoic acid. The convergent biosynthetic pathway established for hygromycin A offers significant versatility for applying the techniques of combinatorial and directed biosynthesis to production of new antibiotics which target the ribosomal peptidyl transferase activity.

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* Corresponding author. Mailing address: Institute for Structural Biology and Drug Discovery, Suite 212B, Biotechnology Park, 800 East Leigh St., Richmond, VA 23219. Phone: (804) 828-7575. Fax: (804) 827-3664. E-mail: kareynol{at}hsc.vcu.edu.

Permanent address: Department of Microbiology, Faculty of Pharmacy, Mansoura University, Mansoura, Egypt.

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Antimicrobial Agents and Chemotherapy, July 2003, p. 2065-2071, Vol. 47, No. 7
0066-4804/03/$08.00+0     DOI: 10.1128/AAC.47.7.2065-2071.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Dhote, V., Gupta, S., Reynolds, K. A. (2008). An O-Phosphotransferase Catalyzes Phosphorylation of Hygromycin A in the Antibiotic-Producing Organism Streptomyces hygroscopicus. Antimicrob. Agents Chemother. 52: 3580-3588 [Abstract] [Full Text]