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Proc Natl Acad Sci U S A. 2009 Jul 28;106(30):12295-300. doi: 10.1073/pnas.0901237106. Epub 2009 Jul 9.

Biosynthesis of the salinosporamide A polyketide synthase substrate chloroethylmalonyl-coenzyme A from S-adenosyl-L-methionine.

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Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0204, USA.


Polyketides are among the major classes of bioactive natural products used to treat microbial infections, cancer, and other diseases. Here we describe a pathway to chloroethylmalonyl-CoA as a polyketide synthase building block in the biosynthesis of salinosporamide A, a marine microbial metabolite whose chlorine atom is crucial for potent proteasome inhibition and anticancer activity. S-adenosyl-L-methionine (SAM) is converted to 5'-chloro-5'-deoxyadenosine (5'-ClDA) in a reaction catalyzed by a SAM-dependent chlorinase as previously reported. By using a combination of gene deletions, biochemical analyses, and chemical complementation experiments with putative intermediates, we now provide evidence that 5'-ClDA is converted to chloroethylmalonyl-CoA in a 7-step route via the penultimate intermediate 4-chlorocrotonyl-CoA. Because halogenation often increases the bioactivity of drugs, the availability of a halogenated polyketide building block may be useful in molecular engineering approaches toward polyketide scaffolds.

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