| Abstract: | Amine oxidase from etiolated seedlings of fenugreek (Trigonellafoenum—graecum) has been isolated by a purification procedureinvolving three chromato—graphic steps. The homogeneousenzyme is of pink colour with a visible absorption maximum at500 nm. The dimeric enzyme (2 75 kDa) is a slightly acidicprotein (pl 6.8) containing 8% neutral sugars. N—ter—minalamino acid sequence of the enzyme shows a high degree of similarityto other plant and microbial copper—containing amine oxidases.The best substrates of the enzyme are aliphatic diamines andsome polyamines, whereas inhibitors are substrate analogues,copper complexing agents, some alkaloids and several other compounds.Spectrophotometric titra—tions with phenylhydrazines demonstratedone reactive carbonyl group per subunit of the enzyme and redox—cyclicquinone staining after native electrophor—esis indicatedthe presence of a quinone cofactor. Differential pulse polarographyshowed the existence of a copper/quinone—containing activesite. The resonance Raman spectroscopy and the pH—dependentshift of the absorption spectrum of the enzyme p—nitrophenylhydrazoneconfirm unambiguously the identity of the cofactor with topaquinone. EPR spectra of the enzyme are in accordance with thoseof tetragonal cupric complexes as known for other copper—containingamine oxidases. Besides the copper, Mn(II)ions were detectedthat partially occupy another metal site in the enzyme, buttheir catalytical importance is unlikely. Key words: Fenugreek, Trigonella foenum—graceum, amine oxidase, topa quinone |
