The Beta-galactosidase system of a novel plant from durian seeds (Durio zibethinus) I. isolation and partial characterization
2001
El-Tanboly, E.E. (National Research Center, Cairo (Egypt). Food Technology and Dairy Dept.)
Bita-galactosidase was partially purified 2.76-fold with a total yield of 21.32% of the original activity by sequential use of ammonium sulfate precipitation and gel filtration through Sephadex G-100 from Durian fruit. A progressive increase in activity of the purified enzyme was observed up to 60 degree centigrade accompanied by a decrease thereafter and the enzyme activity was linear with time at least up to 10 min reaction time, the maximum activity reached it after 20 min and still constant thereafter. An energy of activation of 3.04 Kcal/mole for the enzyme activity was derived from the Arrhenius plot. The optimum pH was 3.0. The purified enzyme started loosing activity above 40 degree centigrade when heated for 10 min. and became completely inactive at 80 degree centigrade. Michael is-constant of (Km) values of 5.5mM and a maximum velocity Vmax) of 0.9 mumoles/mg/min. A Molecular weight (MW) determination of - 1 22 kDa was estimated by gel filtration methods using a Sephadex G-100. Fe+++, Zn++" and Cu++ strongly inhibited the enzyme. However, Mg++ , Ca++ and Mn++ inhibited negligibly.
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