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Partial Purification and Characterization of Cystine Lyase from Cabbage (Brassica oleracea var capitata) ¹

Department of Botany, Ohio University, Athens, Ohio 45701

Cabbage (Brassica oleracea var capitata) leaves were used as a source of cystine lyase. Diethylaminoethyl-cellulose chromatography resolved two peaks of activity, designated I and II.

Cystine lyase I (molecular weight 145,000) and O-acetylserine sulfhydrylase (molecular weight 70,000) were resolved by Bio-Gel A-0.5M chromatography. This isozyme catalyzed an ,-elimination reaction with cystine, cysteine, O-acetylserine, and several S-substituted cysteines. The substrate specificity was similar to previously reported S-alkylcysteine lyases. The elution profiles during purification, and heat inactivation studies indicated that the above reactions were catalyzed by a single protein. The pH optimun with cystine and cysteine as substrate was 8.5 to 9.0, and the K_m values were: cystine (0.3 mM), cysteine (0.3 mM), O-acetylserine (6 mM), and S-methylcysteine sulfoxide (1.8 mM).

Cystine lyase II was resolved into three peaks (molecular weight greater than 500,000, 240,000, and 145,000) using Bio-Gel A-0.5M chromatography. This enzyme degraded L-cystine, L-cysteine, O-acetylserine, S-methylcysteine sulfoxide, and djenkolic acid. The pH optimum with cystine and cysteine was 8.5 to 9.0, and the K_m values were: cystine (0.3 mM), cysteine (0.3 mM), O-acetylserine (12.5 mM), and S-methylcysteine sulfoxide (3.7 mM).

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				P. R. Jones, T. Manabe, M. Awazuhara, and K. Saito A New Member of Plant CS-lyases. A CYSTINE LYASE FROM ARABIDOPSIS THALIANA J. Biol. Chem., March 14, 2003; 278(12): 10291 - 10296. [Abstract] [Full Text] [PDF]