Abstract

GUIJA, Emilio; ARAUCO, Fernando; HAAK-MARES, Hielke  and  SOBERON, Mercedes. Effect of glycerol on catalysis by low molecular weight acid phosphatase from alpaca liver (Lama pacos). An. Fac. med. [online]. 2007, vol.68, n.4, pp.307-313. ISSN 1025-5583.

Objective: To determine the effect of glycerol on hydrolisis of p-nitrophenyl phosphate at pH 5,0 by low molecular weight acid phosphatase from alpaca liver. Design: Experimental analytical study. Setting: Biochemistry and Nutrition Research Center, Faculty of Medicine, Universidad Nacional Mayor de San Marcos, Lima, Peru. Materials: Disodic p-nitrophenyl phosphate salt, glacial acetic acid, glycerol, tricloroacetic acid, sulfuric acid, ammonium molibdate, ascorbic acid, ammonium sulphate, sephadex G-75 (45-120), sulpho ethyl sephadex C-50 and ethylene diaminotetraacetic (EDTA) chemical reactives. Methods: Both Km and Vmax kinetic parameters were determined with p-nitrophenyl phosphate as substrate in presence of different concentrations of glycerol. The rate of formation of products was determined as a function of the concentration of such nucleophile. Main outcome measures: Glycerol effect on p-nitrophenyl phosphate hydrolysis. Results: Glycerol linearly increased p-nitrophenol release at concentrations between 1,16 and 3,49M. Instead, inorganic phosphate formation, the second product, was not modified. Also, Km and Vmax values increased linearly between 0,58 and 2,32 M depending on glycerol concentrations. Conclusions: Analysis of modifications induced by glycerol on Km and Vmax values as well as on liberation velocity of the reaction products suggests a model in which low molecular weight acid phosphatase isolated from alpaca liver catalyses phosphomonoesters hydrolysis through an uni biordered mechanism, with formation of an enzyme-phosphate complex that will be splitted by water or a nucleophile such a glycerol; in this model, k₂ corresponds to a much higher value than k₃ or k₄ N.

Keywords : Acid phosphatase; catalysis; glycerol; kinetics.

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