Oxygen binding to dithionite‐reduced chloroperoxidase

Abstract

Both the kinetics of ferric chloroperoxidase reduction by dithionite and the binding of molecular O to ferrous chloroperoxidase have been studied. The oxyferrous chloroperoxidase decays spontaneously to the ferric enzyme. In addition, the corresponding rapid-scan spectra have been recorded. The reduction reaction is caused by .**GRAPHIC**. with a rate constant of (7.7 .+-. 1.0) .times. 104/M per s. Oxygen binding occurs with a rate constant of (5.5 .+-. 1.0) .times. 105/M per s over the pH range 3.5-6. Oxyferrous chloroperoxidase has a Soret absorption peak at 428 nm and 2 partially resolved peaks at 555 nm and 588 nm. Isosbestic points occur at the following wavelengths: between ferrous and oxyferrous chloroperoxidase at 419, 545, 555 and 580 nm; between oxyferrous and ferric chloroperoxidase at 419, 487, 540, 609 and 682 nm.