The basis of the irreversible inactivation of the vanadium bromoperoxidase (V-BrPO) isolated from the marine alga Ascophyllum nodosum under turnover conditions at low pH (i.e., 15 to 100 mM H2O2, 0.1 KBr, ca. 15 nM V-BrPO in 0.1 M citrate, pH 4) has been investigated. Inactivation under these conditions was found to produce 2-oxohistidine as identified by HPLC using electrochemical detection. F...