A spectrometric study of the Co(2+)-activated ribulose-1,5-bisphosphate carboxylase reaction during turnover and at different pH.
EPR as well as optical absorption studies of the Co(2+)-activated ribulose-1,5-bisphosphate carboxylase/oxygenase under turnover conditions show that the formation of the two detectable intermediates are pH dependent. The amount of one of them, which earlier has been proposed to be a metal coordinated endiol of ribulose-1,5-bisphosphate (Brändén et al. (1987) Biochim. Biophys. Acta 916, 298-303), increased with increasing pH. Distinct optical absorption bands could be assigned to this intermediate and a pH profile could be made. It is therefore proposed that a base with a pKa value of about 8 is responsible for the enzyme-catalysed abstraction of a proton from ribulose-1,5-bisphosphate in order to form the metal coordinated endiol of ribulose-1,5-bisphosphate.
Janson
K
K
Department of Biochemistry and Biophysics, University of Göteborg, Sweden.
Brändén
R
R
D003035:Cobalt / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D004789:Enzyme Activation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010428:Pentosephosphates / Q000378:metabolism; D010940:Plant Proteins; D011522:Protons; D012273:Ribulose-Bisphosphate Carboxylase / Q000302:isolation & purification / Q000378:metabolism*; D013053:Spectrophotometry; D014675:Vegetables / Q000201:enzymology
D010428:Pentosephosphates; D010940:Plant Proteins; D011522:Protons; C054765:rca protein, plant; D003035:Cobalt; D012273:Ribulose-Bisphosphate Carboxylase