The temperature and pH dependence of some properties of p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens.
The free and complexed flavoprotein, p-hydroxybenzoate hydroxylase, was studied by light-absorption, circular-dichroism and fluorescence techniques as a function of the pH. The following compounds served as ligands for the enzyme: p-hydroxybenzoate, p-fluorobenzoate, benzoate, p-aminobenzoate and tetrafluoro-p-hydroxybenzoate. Depending on the technique used, the various ligands exhibit pH-dependent physical properties and dissociation constants. The data can be fitted with pKa values in the range 7.7-7.9. It is suggested that this pKa value belongs to a tyrosine residue in the active center of the enzyme. This assignment is supported by published data and additional experiments.
Van Berkel
W J
WJ
Department of Biochemistry, Agricultural University, Wageningen, The Netherlands.
Müller
F
F
D015109:4-Hydroxybenzoate-3-Monooxygenase / Q000302:isolation & purification / Q000378:metabolism*; D002942:Circular Dichroism; D004795:Enzyme Stability; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D011551:Pseudomonas fluorescens / Q000201:enzymology*; D013053:Spectrophotometry; D013696:Temperature
D006899:Mixed Function Oxygenases; D015109:4-Hydroxybenzoate-3-Monooxygenase