ISSN:
1572-9729
Keywords:
C - P lyase
;
pho regulon
;
phosphonates
;
phosphonatase
;
psi genes
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Energy, Environment Protection, Nuclear Power Engineering
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
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 α-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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00696458
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