Studies on Luciferase from Photobacterium phosphoreum
IX. Further Studies on the Spectroscopic Characteristics of the Enzyme-FMN Intermediates
1977 Volume 81 Issue 4 Pages 1057-1062
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1977 Volume 81 Issue 4 Pages 1057-1062
The absorption and fluorometric changes of the reaction mixture of luciferase-FMNH2 complex with 02 were re-examined. Rapid formation (k2(app)=2.0 s-1 at [O2]=120μM) of an intermediate with a single absorption maximum at 380nm within the range of 350-550nm, and a weak fluorescence at 520nm (≤10% of that of FMN when excited at 380nm) was observed. The absorption and fluorescence spectra and decay rate of the intermediate were estimated by simulation using an analog computer. The decay rate (0.27s-1 at 20°C) was in agreement with that of an obligatory intermediate of the luminescent reaction previously determined by measuring aldehyde-initiated luminescence. The process of decay of X1 to FMN involved another intermediate X1' with spectroscopic characteristics rather similar to those of FMN.
