Phosphonoacetaldehyde hydrolase from Pseudomonas aeruginosa: purification properties and comparison with Bacillus cereus enzyme

Phosphonoacetaldehyde hydrolase (2-oxoethylphosphonate phosphonohydrolase, EC 3.11.1.1) has been purified to electrophoretic homogeneity from cells of Pseudomonas aeruginosa A 237 grown in a culture medium containing 2-aminoethylphosphonate as both phosphorus and carbon sources. The native Mr has been estimated to be 62,000 +/- 2000, using a gel filtration column equilibrated with standard proteins. A subunit of Mr 30,000 +/- 1000 determined in sodium dodecyl sulfate-polyacrylamide gel electrophoresis gives evidence of a homodimeric structure. The enzyme, which catalyzes the C-P bond cleavage of phosphonoacetaldehyde, has a Km value of 210 microM. It is moderately inhibited by methyl-, ethyl-, propyl- and butylphosphonic acids and activated by aminomethyl-, aminoethylphosphonic acids as well as by phosphonoformic, phosphonoacetic and phosphonopropionic acids. Inhibition by orthophosphite is a time-dependent process which exhibits first-order kinetics and is enhanced by the presence of acetaldehyde. Assays for phosphite removal by dilution or dialysis do not reverse the inhibition. Phosphonoacetaldehyde hydrolase inactivation by phosphite ion appears to be inconsistent with the concept of a Schiff base intermediate as proposed for Bacillus cereus enzyme.