Lactobacillus plantarum produces a manganese-containing enzyme with catalase activity, which has been called pseudocatalase to distinguish it from the heme enzyme catalase. Pseudocatalase is an oligomer of subunits each of which contains two manganese atoms which have been shown by ESR measurements to participate in a binuclear cluster. Catalytic activity is inhibited by hydroxylamine and by fluoride in the presence of substrate, hydrogen peroxide. These features suggest that this enzyme is a close relative and a soluble homologue of the binuclear manganese enzyme in the oxygen evolving center of green plant photosynthesis. Dr. Carter has crystallized this enzyme in the presence and absence of a combination of substrate and fluoride that leads to inactivation of the enzyme and attendant bleaching of the prosthetic group. The crystals diffract to high resolution and he has collected three-dimensional native crystal intensity data to 4.5A resolution. He now plans to solve the crystal structures and to analyze them for clues to their reaction mechanism and their relationship to the oxygen evolving center.
