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Kinetic study of enzymatic ?-galactoside hydrolysis in cowpea seeds

Coffigniez F., Briffaz A., Mestres C., Ricci J., Alter P., Durand N., Bohuon P.. 2018. Food Research International, 113 : p. 443-451.

The endogenous alpha-galactosidase activity of cowpea seeds was characterized and modelled assuming Michaelian behavior. The aim is to use the resulting knowledge to optimize alpha-galactoside degradation during the soaking-cooking process. In this study, the alpha-galactosidase enzyme from Wankoun cowpea was extracted and its enzymatic activity was analyzed as a function of temperature, pH and the presence of some inhibitors. Enzymatic activity was optimal around 35?°C and a pH of 5.8. Activation and inactivation energy was evaluated at 50?±?3 and 103?±?9?kJ.mol?1, respectively. The strongest inhibitor was galactose with an inhibition constant KI of 0.28?±?0.03?mM. Incubation of the enzyme extract with alpha-galactosides revealed a 10-h lag phase in the early stages that could be due to low pH, the action of inhibitors including galactose and the biosynthesis of alpha-galactosides. After the lag phase, the degradation of each alpha-galactoside occurred without the appearance of any intermediary product. The degradation of alpha-galactosides was observed with a Km of 1.7?±?0.3?mM for raffinose; 3.6?±?0.6?mM for stachyose and 15.9?±?0.1?mM for verbascose. A long soaking step around 35?°C is suggested to maximize the alpha-galactosides enzymatic degradation.

Mots-clés : cuisson; biosynthèse; enzyme; niébé

Thématique : Physiologie et biochimie végétales; Composition des produits alimentaires

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