Purification and properties of a phosphohydrolase from Enterobacter aerogenes

A phosphohydrolase from Enterobacter aerogenes which hydrolyzes phosphate mono- and diesters has been purified approximately 50-fold to apparent homoeneity and crystallized. The enzyme is produced when the bacteria utilize phosphate diesters as sole phosphorus source. From sedimentation equilibrium experiments the molecular weight of the native enzyme is 173,000; from sodium dodecyl sulfate polyacrylamide gel electrophoresis the subunit molecular weight is 29,000, indicating that the enzyme is hexameric. The hydrolytic activity of the enzyme using both mono- and diesters is maximal at pH 5; THE Km of the enzyme for bis-p-nitrophenyl phosphate is constant from pH 5 to 8.5 whereas that for p-nitrophenyl phosphate increases about 40-fold as the pH increases over the same range. The phosphodiesterase activity is not inhibited by chelating agents but is inhibited by several divalent metal ions. 31-P NMR spectroscopy was used to identify the hydrolysis products of glycoside cyclic phosphates. The enzyme-catalyzed hydrolysis of methyl beta-D-ribofuranoside cyclic 3:5-phosphate yields exclusively the 5-phosphate whereas that of adenosine 3:5-monophosphate yields a 4:1 mixture of 3- and 5- AMP.