Substrate specificity of copper-containing plant amine oxidases

• Published in: Journal of inorganic biochemistry Vol. 101; no. 7; pp. 997 - 1004
• Main Authors: Pietrangeli, P., Federico, R., Mondovì, B., Morpurgo, L.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2007
• Subjects: Amine Oxidase (Copper-Containing) - chemistry; Amine Oxidase (Copper-Containing) - metabolism; Amines - chemistry; Hydrogen-Ion Concentration; Kinetics; Models, Molecular; Molecular Structure; pH dependence; Plant Proteins - chemistry; Plant Proteins - metabolism; Steady-state kinetics; Substrate Specificity; Trihydroxyphenylalanine quinone; Trihydroxyphenylalanine quinone; pH dependence; Steady-state kinetics
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2007.03.014

The steady-state kinetic parameters of the amine oxidases purified from Lathyrus cicera (LCAO) and Pisum sativum (PSAO) seedling were measured on a series of common substrates, previously tested on bovine serum amine oxidase (BSAO). LCAO, as PSAO, was substantially more reactive than BSAO with aliphatic diamines and histamine. The k cat and k cat/ K m for putrescine were four and six order of magnitude higher, respectively. Differences were smaller with some aromatic monoamines. The plot of k cat versus hydrogen ions concentration produced bell-shaped curves, the maximum of which was substrate dependent, shifting from neutral pH with putrescine to alkaline pH with phenylethylamine and benzylamine. The latter substrates made the site more hydrophobic and increased the p K a of both enzyme-substrate and enzyme-product adducts. The plot of k cat/ K m versus hydrogen ion concentration produced approximately parallel bell-shaped curves. Similar p K a couples were obtained from the latter curves, in agreement with the assignment as free enzyme and free substrate p K a. The limited pH dependence of kinetic parameters suggests a predominance of hydrophobic interactions.