Bicarbonate Inhibits Ribulose-1,5-Bisphosphate Carboxylase
AUTOR(ES)
Mächler, Felix
RESUMO
Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) rapidly extracted from leaves of wheat (Triticum aestivum) and purified activated RuBPCO were incubated in the presence and absence of 20 millimolar HCO3− and changes in activation state were followed. Rapid inactivation occurred in the presence, but not in the absence, of HCO3−. Effects of CO2 concentration and pH during preincubation before assay on activation state of RuBPCO were investigated in equilibrium studies. Twenty percent inactivation occurred at high CO2 concentration if pH was high, but not if it was low, suggesting that RuBPCO was inactivated by HCO3−. The inactivation by HCO3− was more rapid than the dissociation of activating CO2 in CO2-free buffer (both in the presence of 20 millimolar MgCl2), suggesting that HCO3− was bound to the active enzyme complex. The dissociation of inactivating HCO3− from the enzyme was slow enough that inhibition could be demonstrated in experiments with HCO3− treatments during preincubation and constant conditions during assay. Inorganic phosphate did not seem to interfere with the binding of HCO3−.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1055600Documentos Relacionados
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