The free radical site in pea seedling copper amine oxidase probed by resonance Raman spectroscopy and generated by photolysis of caged substrate

FEBS Letters

Bisby, Roger H.¹  Tavender, Susan M.²  Parker, Anthony W.²  Johnson, Steven A.¹ 

[1] Department of Biological Sciences, University of Salford, Salford M5 4WT, UK;Laser Support Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK

关键词: Copper amine oxidase;    Resonance Raman spectroscopy;    Free radical;    Caged substrate;    Laser flash photolysis;   

DOI  :  10.1016/0014-5793(96)00045-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Resonance Raman spectra were obtained of the free radical site in substrate reduced anaerobic samples of pea seedling copper amine oxidase (PSAO). The spectra differ significantly from those reported previously for E. coli copper amine oxidase [Moenne-Loccoz et al. (1995) Biochemistry 34, 702]. The spectra were found to be independent of substrate (benzylamine, spermidine or methylamine) used to reduce the TOPA quinone cofactor, however, several of the peaks in the Raman spectrum displayed small shifts on using [¹⁵N]benzylamine, proving incorporation of the substrate nitrogen atom onto the cofactor radical. Changes in the spectrum were also observed when measured in D₂O solution indicating a strongly bound proton in the radical. The spectra were independent of pH values between 5 and 9 and are interpreted as showing that the radical exists as a semiiminoquinone radical monoanion. Benzylamine and phenethylamine have been caged with 2-nitrobenzaldehyde and shown by laser flash photolysis to uncage on a sub-millisecond timescale. Preliminary experiments have shown the formation of the enzyme radical intermediate on laser flash photolysis of 2-nitrobenzyl-caged benzylamine in the presence of enzyme. This should permit time-resolved resonance Raman spectral investigations of the catalytic cycle of copper amine oxidases.

【 授权许可】

Unknown