The purpose of the proposed research is to study the biochemical pathways involved in the metabolism of dihalomethanes. Previous studies conducted in this laboratory have shown that these compounds are metabolized to carbon monoxide, formaldehyde and inorganic halide. The enzymes involved will be characterized with respect to cofactor requirements, substrate specificity, response to inhibitors and time, temperature and pH optima. Studies aimed at elucidating the reaction mechanisms involved are also planned. The hypothesis that monochlorocarbene may be involved as an intermediate in the formation of carbon monoxide will be tested. Finally, enzyme purification studies are proposed. These studies are important from the standpoint of toxicology and the uniqueness of the biotransformation to carbon monoxide.