The enzymic cleavage of the carbon-phosphorus bond: Purification and properties of phosphonatase
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Abstract1.1. Bacillus cereus degrades 2-aminoethylphosphonate by the following pathway: 2.2. Reaction II above involves the enzymic cleavage of the carbon-phosphorus bond and has not been described previously. The enzyme responsible for this reaction has now been purified and studied; we have suggested that it be named “2-phosphonoacetaldehyde phosphonohydrolase”, and that the trivial name be “phosphonatase”.3.3. Phosphonatase shows optimal activity between pH 8 and 9, and has a Km for 2-phosphonoacetaldehyde of 40 μM. Apartfrom 2-phosphonoacetaldehyde, phosphonate shows virtually no activity with any of a number of phosphonates and phosphate esters tested.4.4. The active enzyme is composed of two similar subunits, each of an approximate molecular weight of 33 000–37 000. Mg2+ is required for activity, but this probably helps to maintain the enzyme in its aggregated state rather than play a catalytic role at the active site; no other metals have been shown to be necessary for activity.5.5. Phosphonatase is inhibited by CN−, S2− and SO32−, which suggests that disulphide bridges may be necessary in maintaining the tertiary structure of the activeform of the enzyme.6.6. Orthophosphite, which has been shown previously to abolish the growth of B. cereus on 2-aminoethylphosphonate, inhibits the activity of phosphonatase, but only in the presence of 2-phosphonoacetaldehyde or acetaldehyde. Experiments with [32P]orthophosphite showed that, although the inhibitor was bound tightly to phosphonatase, it did not form a covalent bond with the enzyme.

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