Species differences in monoamine oxidase-A and -B as revealed by sensitivity to trypsin

Monoamine oxidase-A and -B of brain and peripheral tissues of human, dog, rat, and rabbit have been characterized with respect to kinetic parameters and response to limited trypsin treatment. MAO-A in all extracts was inactivated by trypsin to an extent that was species dependent, but not related to the nature of the tissue, to MAO-A/B ratios, or to kinetic parameters. MAO-B activity of human, dog, and rat was unaffected by trypsin under the conditions employed, but rabbit MAO-B was sensitive. Inactivation patterns obtained with the trypsin treatment described in this study provide additional evidence that structures of both MAO-A and MAO-B show species-specific variations.