Substrate specificity of lentil seedling amine oxidase
1996
Medda, R. | Padiglia, A. | Pedersen, J.Z. | Lorrai, A. | Floris, G.
Copper diamine oxidase from lentil (Lens culinaris) seedlings was shown to be able to catalyze the oxidative deamination of a wide range of aliphatic and aromatic monoamine compounds, including some amino acids. Although the catalytic efficiencies were only 1-3% of that measured with the diamine substrate putrescine, they were still comparable to those of specialized monoamine oxidases. In particular, the lentil enzyme oxidized benzylamine and histamine with Km and Vmax values similar to those found for the mammalian enzymes benzylamine oxidase and histaminase. Cysteamine was found to be a substrate of the enzyme, whereas hypotaurine and taurine were found to be neither substrates nor inhibitors of the enzyme. Quite unexpectedly the aminoacids L-ornithine and L-lysine were oxidized by lentil enzyme, and beta-alanine and gamma-aminobutyric acid were oxidized only at high concentrations of enzyme. These results suggest that enzymes normally classified as diamine oxidases could in fact have a more diversified role in metabolism than recognized so far.
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