Biochemistry and Molecular Genetics of the Biosynthesis of the Earthy Odorant Methylisoborneol in Streptomyces coelicolor

Chieh-Mei Wang and David E. Cane
Department of Chemistry, Brown University, Box H, Providence, Rhode Island 02912-9108
J. Am. Chem. Soc., 2008, 130 (28), pp 8908–8909
DOI: 10.1021/ja803639g
Publication Date (Web): June 19, 2008
Copyright © 2008 American Chemical Society

Abstract

Abstract Image

Methylisoborneol (2) is a volatile organic compound produced by a wide variety of Actinomycete soil organisms, myxobacteria, and cyanobacteria. It has an unusually low odor threshold and, together with geosmin, is responsible for the characteristic smell of moist soil as well as unpleasant taste and odor episodes associated with public water supplies and contamination of various foodstuffs, including fish, wine, and beer. Despite considerable interest in detection and remediation of methylisoborneol, the biosynthesis of this methylated monoterpene has been obscure. In Streptomyces coelicolor, the sco7700 and sco7701 genes are shown to correspond to a two-gene operon responsible for methylisoborneol biosynthesis. Both genes have been amplified by PCR and the resulting DNA has been cloned and expressed in Escherichia coli. Incubation of recombinant SCO7701 protein, annotated as a possible C-methyltransferase, with geranyl diphosphate (1) and S-adenosylmethionine gave the previously unknown compound, (E)-2-methylgeranyl diphosphate (3). Incubation of 3 in the presence of Mg2+ with recombinant SCO7700, previously annotated only as a possible metal-binding protein or terpenoid synthase, resulted in the formation of 2-methylisoborneol (2). The steady-state kinetic parameters for both biochemical reactions have been determined. Incubation of geranyl diphosphate and S-adenosylmethionine with a mixture of both SCO7700 and SCO7701 resulted in formation of methylisoborneol (2). Cyclization of 2-methylgeranyl diphosphate (3) to methylisoborneol (2) likely involves the intermediacy of 2-methyllinalyl diphosphate.

View: Full Text HTML | Hi-Res PDF | PDF w/ Links

Tools

History

  • Published In Issue July 16, 2008
  • Article ASAPJune 19, 2008
  • Received: May 15, 2008

Recommend & Share

Related Content

Other ACS content by these authors: