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Title: Role of Disulfide Bridges in Structure-Activity Relationship of Plant Lipases from Wheat germ and Rice bran
Authors: Gopalakrishna, K N
Kaul, Purnima
Kumar, P Ramesh
Prakash, V
Keywords: Lipase;Wheat germ;Disulfide bond;Activity;Conformational stability;Thermal stability
Issue Date: Apr-2002
Publisher: NISCAIR-CSIR, India
Abstract: Disulfide bonds of wheat germ lipase (WGL) and rice bran lipase (RBL) were reduced with sodium borohydride (NaBH4) and dithiothreitol (DTT) under non-denaturing conditions to assess the activity, conformation and stability of reduced form with those of native enzyme by using kinetics, far UV-CD, fluorescence, thermal denaturation studies and microcalorimetric measurements. Activity of reduced lipases was found to decrease in a sequential manner involving atleast two steps in both the lipases. The CD spectrum in the far UV-region indicates that overall conformation was drastically affected upon reduction. A decrease in tryptophanyl fluorescence was observed without any shift in the emission maximum. The apparent thermal denaturation temperature [Tm (app)] of the reduced WGL and RBL was lowered by 6°C and 12°C, respectively, from the native enzyme. Reduction and carboxymethylation of all four cysteines caused extensive unfolding of the enzymes resulting in the loss of activity, conformation and thermal stability significantly indicating that the disulfide bonds have a major role in stabilizing the native conformation and stability of these two lipases.
Page(s): 188-196
ISSN: 0975-0967 (Online); 0972-5849 (Print)
Appears in Collections: IJBT Vol.01(2) [April 2002]

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