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6. Structure and Catalytic Inactivity of the Bacterial Luciferase Neutral Flavin Radical.

Author

Kurfürst, Manfred, Ghisla, Sandro, Presswood, Robert, and Hastings, J. Woodland

Subjects
FLAVINS, BACTERIA, COENZYMES, FLAVOPROTEINS, ENZYMES, COLLOIDS
Abstract

A luciferase-bound neutral flavin semiquinone radical can be formed upon the oxidation of the luciferase- FMNH2 complex by molecular oxygen. This species can also be formed anaerobically by comproportionation of FMN and FMNH2 in the presence of luciferase. The radical is kinetically stable (t1/2 ≈ 20 h at 0 °C in air: the Arrhenius ΔHdecay= being about 170 kJ/mol) and can be prepared in pure form by Sephadex G-25 chromatography at 0-4 C. The pure enzyme-bound radical is inactive for light emission either with or without aldehyde, and is not in (relevantly rapid) equilibrium with the luciferase 4a-peroxyflavin, the active intermediate in the bioluminescent reaction. [ABSTRACT FROM AUTHOR]

Published
1982
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10. Oxygen dependent and independent steps in luciferase-FMNH2oxidation

Author

Presswood, Robert and Hastings, J.W.

Abstract

Upon reaction of luciferase-FMNH2with oxygen a complex series of absorbance changes occur, leading to the formation of a stable (t12about 35 min at 2°) dihydroflavin peroxyluciferase intermediate. Observed at 380, 445, or 600 nm, there is first a rapid absorbance increase which is oxygen-concentration dependent (k ⋍ 106M−1s−1. Following this there are two oxygen independent steps, first a slow absorbance decrease (k = 4.3 s−1) and then an even slower increase (k = 0.55 s−1). The dihydroflavin peroxide is not expected to have absorption at 600 nm and is thus postulated to be in equilibrium with some flavin species which does absorb in the red.

Published
1978
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