Molecular Genetics of Carbon-Phosphorus Bond Cleavage in Bacteria

Biodegradation. 1994 Dec;5(3-4):175-84. doi: 10.1007/BF00696458.

Abstract

Phosphonates (Pn) are a large class of organophosphorus molecules that have direct carbon-phosphorus (C-P) bonds in place of the carbon-oxygen-phosphorus ester bond. In bacteria two pathways exist for Pn breakdown for use as a P source: the phosphonatase and C-P lyase pathways. These pathways differ both in regard to their substrate specificity and their cleavage mechanism. The phosphonatase pathway acts on the natural Pn alpha-aminoethylphosphonate (AEPn). In a two-step process it leads to cleavage of the C-P bond by a hydrolysis reaction requiring an adjacent carbonyl group. In contrast the C-P lyase pathway has a broad substrate specificity. It leads to cleavage of substituted Pn (such as AEPn) as well as unsubstituted Pn by a mechanism involving redox or radical chemistry. Due to its broad substrate specificity, the C-P lyase pathway is generally thought to be responsible for the breakdown of Pn herbicides (such as glyphosate) by bacteria. As a way to gain a more in-depth understanding of these Pn degradative pathways, their respective genes have been isolated and characterized. In the absence of a biochemical assay for the C-P lyase pathway such molecular approaches have been especially valuable. The roles of individual genes have been inferred from DNA sequence analysis and mutational effects. Genes for the C-P lyase pathway exist in a fourteen-gene operon that appears to encode both a binding protein-dependent Pn transporter and a C-P lyase. Genes for the phosphonatase pathway also exist in a gene cluster containing Pn uptake and degradative genes. A combination of biochemistry, molecular biology, and molecular genetics approaches has provided more detailed understanding of the mechanisms of C-P bond cleavage. Such basic information may provide a new handle for improvement of Pn degradation capabilities in bacteria, or in other cells in which the respective genes may be introduced and expressed.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Bacteria / chemistry
  • Bacteria / enzymology
  • Bacteria / genetics
  • Bacteria / metabolism*
  • Base Sequence
  • Biodegradation, Environmental
  • Carbon / chemistry
  • Carbon / metabolism*
  • Cloning, Molecular
  • DNA, Bacterial
  • Hydrolases / genetics
  • Hydrolases / metabolism
  • Hydrolysis
  • Lyases / genetics
  • Lyases / metabolism
  • Molecular Sequence Data
  • Multigene Family
  • Phosphorus / metabolism*

Substances

  • DNA, Bacterial
  • Phosphorus
  • Carbon
  • Hydrolases
  • phosphonoacetaldehyde hydrolase
  • Lyases
  • carbon-phosphorus lyase