[Artifactual multiple forms of beta-cyanoalanine synthase from white lupine]

The three active forms of beta-cyanoalanine synthase (EC 4.4.1.9) from white lupine seedlings were obtained in a homogeneous state and some physico-chemical and catalytic properties of the enzyme, i.e. isoelectric points, molecular weight, amino acid composition, Km, substrate and cosubstrate specificity, etc., were studied. The three enzyme forms obtained were shown to differ insignificantly in their properties. However, their Km values for the substrates are a little higher than those for the enzyme isolated in the presence of the esterolytic protease inhibitor, namely diisopropyl fluorophosphate. A conclusion is drawn that the three active forms of beta-cyanoalanine synthase are produced under the action of proteases in the course of purification and are, accordingly, artefacts.