Unique reaction of a barley peroxidase with hydrogen peroxide.

The reaction of barley peroxidase BP 1 with H2O2 is markedly different from that of other peroxidases. Saturation kinetics and a strong pH dependence over the accessible pH range from 3.09 to 5.08 are observed. At pH 3.8, native BP 1 has maxima at 401, 498 and 635 nm, cpd 1 at 403 nm, and cpd II at 407 and 521 nm with a shoulder at 553 nm. Both cpds I and II appear to be incompletely formed. Isosbestic points between native BP 1 and cpd I occur at 365 and 416 nm, while an isosbestic point in the Soret region between cpd I and cpd II has been observed at 410 nm. Between cpd II and a not yet identified intermediate isosbestic points have been observed at 408, 455 and 526 nm.