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

David I. Hall and Ivan K. Smith
Plant Physiology
Vol. 72, No. 3 (Jul., 1983), pp. 654-658
Stable URL: http://www.jstor.org/stable/4268089
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Partial Purification and Characterization of Cystine Lyase from Cabbage (Brassica oleracea var capitata)
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Abstract

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 sulfhy-drylase (molecular weight 70,000) were resolved by Bio-Gel A-0.5M chromatography. This isozyme catalyzed an α,β-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 Km 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 Km 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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