Glycosidases of turnip leaf tissues
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Four myrosinase (β-thioglucosidase EC. 184.108.40.206) and seven disaccharase (β-fructofuranosidase, EC. 220.127.116.11) isoenzymes were isolated from turnip leaves. The most active enzymes were isolated in pure form. Myrosinase and disaccharase mol wt was 62.0 × 103 and 69.5 × 103 dalton, respectively, on the basis of gel filtration on Sephadex G-200.
Myrosinase pH profile showed high activity between pH 5 and 7 with the optimum at pH 5.5. The purified enzyme was heat-stable for 60 min at 30°C with only loss of 24% of activity. Its activity is strongly inhibited (100%) by Pb2+, Ba2+, Cu2+ and Ca2+ ions, and activated (70%) by EDTA at 0.04M. The pure enzyme failed to hydrolyze amylose, glycogen, lactose, maltose, and sucrose. TheK m andV max values of myrosinase using sinigrin as specific substrate was 0.045 mM and 2.5 U, respectively.
The maximal activity of disaccharase enzyme was obtained at pH 4–5 and 35–37°C. The enzyme was heat-stable at 30°C for 30 min with only 10% loss of its activity. Its activity is strongly activated (70–240%) by Ca2+, Ba2+, Cu2+, and EDTA at 0.01M. The enzyme activity is specific to the disaccharide sucrose and failed to hydrolyze other disaccharides (maltose and lactose). TheK m andV max of disaccharase were 0.123 mM and 3.33 U, respectively.
Index EntriesTurnip leaves myrosinase (β-thioglucosidase) disaccharase (β-fructofuranosidase) Sephadex G-200
- 2.Jwanny, E. W. and El-Sayed, S. T. (1993),Appl. Biochem. Biotechno. in press.Google Scholar
- 3.Lonnerdal, B. and Janson, J-C. (1973),Biochimica et Biophysica Acta 315, 421.Google Scholar
- 5.Bones, A. M. and Slupphaug, G. (1989),J. Plant Physiol. 134, 722.Google Scholar
- 6.Bones, A. M. and Thangstad, O. P. (1991), Proceedings of the 8th International Rapessed Congress, Saskaton, Canada, in press.Google Scholar
- 9.Vasil’ena, Z. V. (1956),Lenia I, 133.Google Scholar
- 10.Thorsell, W. (1959),Arkiv. Kemi. 14, 429.Google Scholar
- 11.Nigoro, H. and Hirano, S. (1962),Kagaku to Kaguo (Osaka) 36, 475.Google Scholar
- 12.El-Sayed, S. T., Moharib, S., and Jwanny, E. W. (1993),International Food Science and Technology in press.Google Scholar
- 13.Somogyi, M. (1952),J. Biol. Chem. 195, 19.Google Scholar
- 14.Nelson, N. (1944),J. Biol. Chem. 153, 375.Google Scholar
- 15.Lowry, O. L., Roserough, N. J., Farr, A. L., and Randall, R. J. (1951),J. Biol. Chem. 193, 265.Google Scholar
- 16.Warburg, O. and Christian, W. (1942),Biochem. Z. 310, 384.Google Scholar
- 17.Thies, W. (1988),Fat Sci. Technol. 90, 311.Google Scholar
- 19.Andrews, R. (1964),Biochem. J. 96, 595.Google Scholar
- 20.Flodin, P. and Porath, J. (1961),J. Chromatog. 13, 328.Google Scholar
- 25.Sandvick, O. (1962), Studies on casein precipitating enzymes of aerobic and faculatively anerobic bacteria. Thesis Veterinary College of Norway, Oslo, p. 116.Google Scholar