
%0 Journal Article
%A Cox, Sean D. 
%A Andrews, T. John 
%A Lilley, Ross McC. 
%T Chemiluminescence of Mn <emph type="7">2+</emph>-activated Rubisco: temperature and pH responses differ between L<emph tye="8">2</emph> and L<emph tye="8">8</emph>S<emph tye="8">8</emph> forms, and inhibitors provide no evidence for involvement of active oxygen species
%J Functional Plant Biology
%D 1999/08/27
%V 26
%N 5
%P 475-484
%K manganese, luminescence, ribulose-bisphosphate carboxylase, oxygenase, singlet oxygen.
%R https://doi.org/10.1071/PP99032
%U https://www.publish.csiro.au/paper/PP99032 
%X Chemiluminescence associated with the oxygenase activity of Mn 2+ -activated D-ribulose-1,5- bisphosphate carboxylase/oxygenase (Rubisco) was investigated using the L 8 S 8 enzymes from spinach and Synechococcus PCC6301, and the L 2 enzyme from Rhodospirillum rubrum. Chemi-luminescence was measured with a luminometer and oxygenase activity with an oxygen electrode. The relative luminescence yield (light emitted per oxygenase turnover) in the steady-state at pH 8.1 was highest with spinach Rubisco; the enzymes from Synechococcus and R. rubrum exhibited approximately one half and one fifth, respectively, of the spinach value. The relative luminescence yield from the L 8 S 8 enzymes was unaffected by temperature (20&#8211;40&#176;C) and pH (7.6&#8211;9.0). In contrast, the luminescence yield of R. rubrum Rubisco varied with temperature and pH, and its O 2 -consuming activity exhibited a lower activation energy than that of the L 8 S 8 enzymes. The singlet O 2 -reactive compounds diazabi-cyclo&#91; 2.2.2&#93;octane and 10,10&#8242;-dimethyl-9,9&#8242;-biacridinium dinitrate (lucigenin) had no effect on chemi-luminescence. Other compounds tested inhibited chemiluminescence but also inhibited O 2 consumption. The inhibition of chemiluminescence of spinach Rubisco required several seconds to exert its maximal effect, implying that the inhibitors had access to the active site only at a particular stage of the catalytic cycle. The data are consistent with the Mn 2+ ion at the active site being the source of the luminescence. 
