Effect of pH on the interaction of benzoate and D-amino acid oxidase

S Quay, V Massey


The kinetic and equilibrium dissociation constants of the reversible binding of benzoate to hog kidney D-amino acid oxidase (DAAO) were studied at 19 degrees C over the pH range 5.3-10.5 by means of a stopped-flow apparatus and spectrophotometric titrations. A simple bimolecular reaction of the form second order-first order was observed; a two-step reaction was seen. Analysis of the pH dependence of the bimolecular rate constants and equilibrium dissociation constants is consistent with three ionizable groups which are important for benzoate binding. The pK values of the enzyme-related ionization are 6.3, 9.2, and 9.6. Analysis of the change in extinction coefficient at 360 nm indicates the pK of 9.6 can be assigned to the 3-imino group of the enzyme-bound flavin. The effect of benzoate on the apparent pK for the ionization of the 3-imino group of the enzyme-bound Fad has been reexamined. The presence of benzoate causes an apparent shift of this ionization from a pK value of 9.6 to 10.7.


Sep 1, 1987·European Journal of Biochemistry·M A VanoniS Ronchi
Mar 1, 1989·European Journal of Biochemistry·M Pilone SimonettaS Ronchi
Jul 16, 1980·Biochemical and Biophysical Research Communications·T NishinoV Massey
Mar 20, 1990·Biochemistry·P MacherouxV Massey
Aug 16, 1996·The Journal of Biological Chemistry· Murthy YVSN, V Massey
Mar 12, 2005·The Journal of Biological Chemistry·Weiwei ShiR Hille
May 16, 1998·The Journal of Biological Chemistry·Y V Murthy, V Massey

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