Bacterial carbon-phosphorus lyase: products, rates, and regulation of phosphonic and phosphinic acid metabolism

Abstract

Carbon-phosphorus bond cleavage activity, found in bacteria that utilize alkyl-and phenylphosphonic acids,has not yet been obtained in a cell-free system. Given this constraint, a systematic examination of in vivo C-P lyase activity has been conducted to develop insight into the C-P cleavage reaction. Six bacterial strains were obtained by enrichment culture, ideptified, and characterized with respect to their phosphonic acid substrate specificity. One isolate, Agrob4acterium radiobacter, was shown to cleave the carbon-phosphorus bond of a wide range of substrates, including fosfomycin, glyphosate, and dialkyl phosphinic acids. Furthermore, this organism processed vinyl-, propenyl-, and prQpynylphosphonic acids, a previously uninvestigated group, to ethylene, propene, and propyne, respectively. A determination of product stoichiometries revealed that both C-P bonds of dimethylphosphinic acid are cleaved quantitatively to methane and, furthermore, that the extent of C-P bond cleavage correlated linearly with the specific growth rate for a range of substrates. The broad substrate specificity of Agrobacterium C-P lyase and the comprehensive characterization of the in vivo activity make this an attractive system for further biochemical and mechanistic experiments. In addition, the failure to observe the activity in a group of gram-positive bacteria holds open the possibility that a periplasmic component may be required for in vivo expression of C-P lyase activity.Living systems contain organophosphorus mostly in the form of oxygen esters, diesters, and anhydrides of phosphoric acid. However, phosphonic acids, a class of organophosphorus compounds containing a direct carbon-phosphorus bond, are also found in nature (14, 21). The initial discovery of a natural phosphonic acid product, 2-aminoethylphosphonic acid, in 1959 (18) is relatively recent compared with the history of research in biological organophosphate esters. Since that time dozens of naturally occurring C-P compounds have been discovered (17). The biosynthesis of the C-P bond has been documented in protozoa, fungi, and molluscs (16, 37). The importance of C-P bonds in these invertebrates is underscored by the observation that 50 to 75% of the cilia phospholipids of Tetrahymena are phosphonolipids (22).Given the biosynthetic accessibility of the C-P linkage it is almost axiomatic that bacteria would have evolved the ability to catabolize phosphonic acids. Indeed, by enrichment culture bacteria have been obtained that utilize 2-aminoethylphosphonic acid, the most abundant naturally occurring phosphonic acid, as the sole source of phosphorus, nitrogen, and carbon (4). The biochemistry of this process was first investigated in Bacillus cereus, where 2-aminoethylphosphonic acid was shown to undergo transamination to yield phosphonoacetaldehyde followed by hydrolysis to acetaldehyde and Pi (25). The hydrolytic cleavage step is catalyzed by phosphonoacetaldehyde hydrolyase (26), an enzyme given the trivial name of phosphonatase (equation 1).2-phosphonatase OHCCH...

Purification and Characterization of a Novel Phosphorus-oxidizing Enzyme from Pseudomonas stutzeri WM88

“…The mechanism of the broad substrate specificity enzyme carbon-phosphorus lyase probably does not involve a simple hydrolytic mechanism, based on the examination of various substrates and their products (18). However, the mechanism of this enzyme remains obscure because in vitro activity of the enzyme has never been achieved, despite numerous attempts and the identification and characterization of the genes that encode it (18,19).…”

“…The mechanism of the broad substrate specificity enzyme carbon-phosphorus lyase probably does not involve a simple hydrolytic mechanism, based on the examination of various substrates and their products (18). However, the mechanism of this enzyme remains obscure because in vitro activity of the enzyme has never been achieved, despite numerous attempts and the identification and characterization of the genes that encode it (18,19).Two biochemical studies of enzymes that presumably do catalyze direct phosphorus redox reactions have been reported. Malacinski and Konetzka (20,21) did cell suspension studies and partially purified an NAD-dependent phosphite oxidoreductase from Pseudomonas fluorescens 195, and Heinen and Lauwers (8) did cell suspension studies with a hypophosphite oxidase from Bacillus caldolyticus.…”

Insights into the Mechanism of Catalysis by the P−C Bond-Cleaving Enzyme Phosphonoacetaldehyde Hydrolase Derived from Gene Sequence Analysis and Mutagenesis

“…Presently, three P-C bond-cleaving enzymes are known. The C-P lyase, which has a very broad substrate specificity, cleaves the C-P bond homolytically, yet ultimately produces inorganic phosphate and the corresponding hydrocarbon (11)(12)(13)(14). The C-P lyase is the most widely distributed bacterial phosphonate-degrading enzyme, and it appears to serve as the main route for inorganic phosphate extraction from environmental phosphonates.…”

At the Intersection of Chemistry, Biology, and Medicine

“…This reaction is relevant to the turnover of natural phosphonolipids, for example, those found in tetrahymena membranes and also in enzymatic degradation of phosphonate herbicides such as Roundup (28,29). In collaboration with Barry Wanner we determined a string of C-P lyase-requiring genes in E. coli (30) and with Heinz Floss established that a radical mechanism was in play for simple substrates such as branched alkylphosphonates.…”