PURIFICATION AND PROPERTIES OF β-CYANO-L-ALANINE SYNTHASE FROM SPINACIA OLERACEA

Article abstract of DOI:10.1016/0031-9422(88)80087-6

β-Cyano-L-alanine synthase was purified ca 6200-fold to homogeneity from the leaves of spinach (Spinacia oleracea).The purified enzyme has an apparent M_r of 60 000 and can be dissociated into identical subunits of M_r 30 000.The subunits each contain one molecule of pyridoxal 5'-phosphate.The K_m value is 2.3 mM for L-cysteine and 0.73 mM for cyanide. β-Cyano-L-alanine synthase from S. oleracea also catalyses the formation of some S-substituted L-cysteines and some heterocyclic β-substituted alanines from L-cysteine or O-acetyl-L-serine.The specificity of these additional catalytic activities of the purified enzyme are compared with those of cysteine synthase purified from the same plant, and with those of β-cyano-L-alanine synthase purified from other sources.Some other properties, including the amino acid composition of the purified enzyme, are also described. - Key Word Index: Spinacia oleracea; Chenopodiaceae; spinach; β-cyano-L-alanine synthase; cysteine synthase; enzyme purification; amino acid composition; L-cysteine; O-acetyl-L-serine; β-cyano-L-alanine; heterocyclic β-substituted alanines.