Biochemical Characterization of Purified Esterase from Soybean (Glycine max) Seed
2015
de Barros, Márcio | Macedo, Gabriela Alves
Alkaline esterase (carboxylic-ester hydrolases; EC 3.1.1.1) extracted from germinated soybean seeds (Glycine max) was purified approximately 3.6 times by chromatography in a DEAE-cellulose anion exchange column and filtration in Sephadex G100 gel. The molecular mass of the enzyme was estimated at 45 kDa by gel electrophoresis (SDS-PAGE). The purified enzyme showed a specific activity of 5.6 U mg⁻¹using p-nitrophenyl butyrate as substrate. The esterase showed optimal activity at 47 °C in moderately alkaline pH, low stability in temperatures higher than 50 °C, and high stability at pH values between 6 and 9.5. The Ca²⁺and Co²⁺ions proved to have a positive effect on enzyme activity; however, Hg²⁺completely inhibited esterase activity. Using p-nitrophenyl butyrate as substrate, the enzyme showed a Kₘof 0.39 mM, Vₘₐₓof 31.5 mM mg⁻¹ min⁻¹and kcₐₜ7.60 × 10⁶ s⁻¹. Regarding substrate affinity, the enzyme showed greater activity for substrates containing short-chain fatty acids, especially p-nitrophenyl acetate. Such characteristics give the enzyme great potential for application in the production of low molecular weight esters, in the food industry, and in chemical products. This enzyme is another new member of the family of lipases and esterases from vegetable seeds with high activity and stability in alkaline pH.
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