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Mol Syst Biol. 2010 Nov 30;6:436. doi: 10.1038/msb.2010.88.

Three serendipitous pathways in E. coli can bypass a block in pyridoxal-5'-phosphate synthesis.

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  • 1Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA.

Abstract

Bacterial genomes encode hundreds to thousands of enzymes, most of which are specialized for particular functions. However, most enzymes have inefficient promiscuous activities, as well, that generally serve no purpose. Promiscuous reactions can be patched together to form multistep metabolic pathways. Mutations that increase expression or activity of enzymes in such serendipitous pathways can elevate flux through the pathway to a physiologically significant level. In this study, we describe the discovery of three serendipitous pathways that allow synthesis of pyridoxal-5'-phosphate (PLP) in a strain of E. coli that lacks 4-phosphoerythronate (4PE) dehydrogenase (PdxB) when one of seven different genes is overexpressed. We have characterized one of these pathways in detail. This pathway diverts material from serine biosynthesis and generates an intermediate in the normal PLP synthesis pathway downstream of the block caused by lack of PdxB. Steps in the pathway are catalyzed by a protein of unknown function, a broad-specificity enzyme whose physiological role is unknown, and a promiscuous activity of an enzyme that normally serves another function. One step in the pathway may be non-enzymatic.

Comment in

  • Metabolism gets lucky. [Mol Syst Biol. 2010]
PMID:
21119630
[PubMed - indexed for MEDLINE]
PMCID:
PMC3010111
Free PMC Article

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