Open AccessThe temperature and pH dependence of some properties of p ‐hydroxybenzoate hydroxylase from Pseudomonas fluorescens
Author(s) -
BERKEL Willem J. H.,
MÜLLER Franz
Publication year - 1989
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1989.tb14556.x
Subject(s) - hydroxybenzoate , chemistry , flavoprotein , dissociation constant , circular dichroism , pseudomonas fluorescens , enzyme , stereochemistry , residue (chemistry) , tyrosine , crystallography , biochemistry , receptor , biology , bacteria , genetics
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 p K a values in the range 7.7 – 7.9. It is suggested that this p K a value belongs to a tyrosine residue in the active center of the enzyme. This assignment is supported by published data and additional experiments.