Abstract
Partially purified enzyme from guinea-pig leucocytes has been shown to have properties similar to both guinea-pig and rabbit liver aldehyde oxidase. The presence of molybdenum in the leucocyte enzyme has been demonstrated and substrate oxidation by either guinea-pig enzyme was found to be completely inhibited by menadione, a potent inhibitor of rabbit liver aldehyde oxidase. The leucocyte enzyme resembles the guinea-pig liver enzyme in terms of substrate specificity but there is considerable variation in substrate oxidation rates between the two species.