Pulmonary O-methyl transferases

An investigation in vitro of pulmonary O-methyl transferases revealed the presence of microsomal phenol-O-methyl transferase and soluble and microsomal catechol-O-methyl transferases in guineapig lung tissue. Both phenol and catechol transferases also were detected in rat and rabbit lung tissue. Substrates of guinea-pig pulmonary phenol-O-methyl transferase included phenols, cresols and xylenols. but not alcohols and amines. Catechol-O-methyl transferases from both subcellular sources were found to have similar pH optima, magnesium ion requirements, K_m values, and utilized norepinephrine, isoproterenol and dopamine as substrates, but not metaproterenol and salbutamol. These data for the pulmonary enzymes are similar to published values for liver O-methyl transferases.