A bacterial strain, Pseudomonad EF group 70B, containing a high catalase-like activity was found in process water (white water) from pulp using recycled fibers. The enzyme was purified and characterized, and found to be a hydroperoxidase. The active enzyme has an apparent molecular mass of about 153 kDa with two identical subunits and a pi value of 4.7. It has a rather sharp pH optimum for catalase activity at 6.0 hut exhibits catalase, peroxidase and brominating activities over a broad pH range from 4 to 8. It was not inhibited by 3-amino-1,2,4-triazole. Peroxidase-like activity was found when adding o-dianisidine, pyrogallol, guaiacol and 4-,aminoantipyrine. Brominating activity was noticed using monochlorodimedone as a substrate. The absorption spectrum exhibited a Soret band at 403 nm. Upon reduction with dithionite the Soret peak decreased and shifted to 436 nm. Pyridine hemochrome spectra indicated the presence of a protophorfyrin IX heme group and the enzyme was inhibited by the known heme ligands cyanide and azide. N-terminal amino acid analysis gave the sequence STEVKLPYAVAGSGTTILDAFPGE, which showed no homology with those of known catalases or peroxidases. It is concluded that the enzyme is a novel type of catalase-peroxidase or, more specifically, a bromoperoxidase-catalase : and that future developments of inhibitors of hydrogen peroxide-degrading activities in white water may be based on this enzyme and other catalase-peroxidases,