Substrate specificity of copper-containing plant amine oxidases.
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)/Km 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 pK(a) of both enzyme-substrate and enzyme-product adducts. The plot of k(cat)/Km versus hydrogen ion concentration produced approximately parallel bell-shaped curves. Similar pK(a) couples were obtained from the latter curves, in agreement with the assignment as free enzyme and free substrate pK(a). The limited pH dependence of kinetic parameters suggests a predominance of hydrophobic interactions.
Pietrangeli
P
P
Department of Biochemical Sciences, A. Rossi Fanelli, University of Rome La Sapienza, P.le A. Moro 5, 00185 Rome, Italy. paola.pietrangeli@uniromal.it
Federico
R
R
Mondovì
B
B
Morpurgo
L
L
D006631:Amine Oxidase (Copper-Containing) / Q000737:chemistry / Q000378:metabolism*; D000588:Amines / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
D000588:Amines; D010940:Plant Proteins; D006631:Amine Oxidase (Copper-Containing)