title: The generation of an organic free radical in substrate-reduced pig kidney diamine oxidase-cyanide.
abstract: When the cyanide complex of the copper protein, pig kidney diamine oxidase, is reduced anaerobically by cadaverine (1,5-diaminopentane), the broad, 480 nm, absorption band characteristic of the resting enzyme is bleached and a new absorption spectrum with features at 457, 429, 403 (shoulder), 360 (shoulder) and 332 nm appears. Concomitantly, the EPR spectrum of the enzyme Cu(II)-CN complex decreases in intensity and a new signal is observed that is attributable to an organic free radical. The g values and hyperfine splittings are similar to those previously assigned to a free radical observed when the cyanide complex of lentil seedling diamine oxidase is reacted with the substrate p-dimethylaminomethylbenzylamine [(1984) FEBS Lett. 176, 378-380]. The optical absorption and EPR spectra of the organic radical observed in both proteins are consistent with the same semiquinone-type structure, as expected if pyrroloquinolinequinone (PQQ) is the bound cofactor found in both enzymes.
mesh_terms: D006631:Amine Oxidase (Copper-Containing) / Q000378:metabolism*; D000818:Animals; D003486:Cyanides / Q000378:metabolism*; D005609:Free Radicals; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D045542:PQQ Cofactor; D011804:Quinolines / Q000378:metabolism; D013053:Spectrophotometry; D013552:Swine
chemical_list: D003486:Cyanides; D005609:Free Radicals; D011804:Quinolines; D045542:PQQ Cofactor; D006631:Amine Oxidase (Copper-Containing)