PURIFICATION AND CHARACTERIZATION OF BETA-CYANOALANINE SYNTHASE FROM CASSAVA TISSUES

The occurrence of the beta-cyanoalanine pathway for detoxication of cy anide in cassava was examined by studying the activity of beta-cyanoal anine synthase (beta-CAS) [EC.4.4.1.9]: which is the major enzyme invo lved in the conversion of cyanide to beta-cyanoalanine. beta-CAS was p artially purified from cassava leaf, rind and tuber. Its specific acti vity in the tuber was significantly greater than that in the leaf and rind. The purified enzyme appeared as a single band with M-r of 50 k i n SDS-PAGE. On gel filtration over Sephadex G-150, the enzyme was elut ed as a single peak with an average M-r of 51 k. beta-CAS from all thr ee tissues had an optimum pH of 9.0 and showed maximum activity at 30 degrees and the K-m (cyanide) was similar. The presence of serine, an alternate substrate for the enzyme did not affect the utilisation of c ysteine for the formation of beta-cyanoalanine. (C) 1997 Elsevier Scie nce Ltd.