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The primary structure of bovine monoamine oxidase type A. Comparison with peptide sequences of bovine monoamine oxidase type B and other flavoenzymes.

ABSTRACT: We have isolated cDNA clones believed to encompass the full-length coding sequences for a subunit of bovine monoamine oxidase type A (MAO-A). The clones code for an apoprotein of 527 amino acid residues corresponding to a molecular mass of 59,806 Da. The inferred protein sequences show an overall similarity of 68% with partial amino acid sequences of bovine type B MAO (about 41% of the total sequence), as well as a greater similarity (greater than 90%) with some regions including that for the published sequence of the flavin-binding region. Sequence comparisons indicate that these two forms of MAO are encoded by distinct genes. Comparison of this sequence with other flavoenzymes showed similarity with regions associated with non-covalent flavin-binding sites. Analysis of mRNAs coding for MAO enzymes showed a heterogeneity of transcripts consistent with several different forms of monoamine oxidase.

SUBMITTER: Powell JF

PROVIDER: S-EPMC1138524 | biostudies-other | 1989 Apr

REPOSITORIES: biostudies-other

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Project description:Background: Methylxanthines including caffeine and theobromine are widely consumed compounds and were recently shown to interact with bovine copper-containing amine oxidase. To the best of our knowledge, no direct demonstration of any interplay between these phytochemicals and human primary amine oxidase (PrAO) has been reported to date. We took advantage of the coexistence of PrAO and monoamine oxidase (MAO) activities in human subcutaneous adipose tissue (hScAT) to test the interaction between several methylxanthines and these enzymes, which are involved in many key pathophysiological processes. Methods: Benzylamine, methylamine, and tyramine were used as substrates for PrAO and MAO in homogenates of subcutaneous adipose depots obtained from overweight women undergoing plastic surgery. Methylxanthines were tested as substrates or inhibitors by fluorimetric determination of hydrogen peroxide, an end-product of amine oxidation. Results: Semicarbazide-sensitive PrAO activity was inhibited by theobromine, caffeine, and isobutylmethylxanthine (IBMX) while theophylline, paraxanthine, and 7-methylxanthine had little effect. Theobromine inhibited PrAO activity by 54% at 2.5 mM. Overall, the relationship between methylxanthine structure and the degree of inhibition was similar to that seen with bovine PrAO, although higher concentrations (mM) were required for inhibition. Theobromine also inhibited oxidation of tyramine by MAO, at the limits of its solubility in a DMSO vehicle. At doses higher than 12 % v/v, DMSO impaired MAO activity. MAO was also inhibited by millimolar doses of IBMX, caffeine and by other methylxanthines to a lesser extent. Conclusions: This preclinical study extrapolates previous findings with bovine PrAO to human tissues. Given that PrAO is a potential target for anti-inflammatory drugs, it indicates that alongside phosphodiesterase inhibition and adenosine receptor antagonism, PrAO and MAO inhibition could contribute to the health benefits of methylxanthines, especially their anti-inflammatory effects.

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The primary structure of bovine monoamine oxidase type A. Comparison with peptide sequences of bovine monoamine oxidase type B and other flavoenzymes.

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