Insights into the interaction of human liver arginase with tightly and weakly bound manganese ions by chemical modification and site-directed mutagenesis studies.
Diethyl pyrocarbonate (DEPC) caused a loss in the ability of inactive subunits of wild-type and H141F mutant human liver arginase (EC 3.5.3.1) to be reactivated by Mn(2+). The effect was reversed by hydroxylamine and involved a residue with a pK(a) of 6.5+/-0.1. Half activation with Mn(2+) was sufficient for total resistance of H141F and full activation was not impeded by a previous incubation of the half-active species with DEPC. The H101N and H126N mutants expressed 60 and 82% of the wild-type activity, respectively, without changes in K(m) for arginine or K(i) for lysine inhibition. After dialysis against EDTA, H126N was inactive in the absence of added Mn(2+) and contained <0.1 Mn(2+)/subunit, whereas H101N was half active and contained 1.2+/-0.1 Mn(2+)/subunit. Results support the concept that a weakly bound metal ion is needed only for conversion of active species to a more active active state.
Orellana
María S
MS
Departamento de Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile.
López
Vasthi
V
Uribe
Elena
E
Fuentes
Marcia
M
Salas
Mónica
M
Carvajal
Nelson
N
D001119:Arginase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001120:Arginine; D004047:Diethyl Pyrocarbonate / Q000737:chemistry; D004789:Enzyme Activation; D006639:Histidine / Q000235:genetics; D006801:Humans; D019811:Hydroxylamine / Q000737:chemistry; D008099:Liver / Q000201:enzymology*; D008345:Manganese / Q000737:chemistry / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation
D019811:Hydroxylamine; D008345:Manganese; D006639:Histidine; D001120:Arginine; D001119:Arginase; D004047:Diethyl Pyrocarbonate