Avaliação da atividade da lipoxigenase na castanha do Brasil (Bertholletia Excelsa)

Abstract

To determine the optimum conditions of lipoxygenase activity (LOX) of the Brazil nut (Bertholletia excelsa) was considered the activity accordinh to pH in buffer solutions (pH 4.00, 5.00, 6.00, 6.50, 7.00, 8.00 and 9.00), varying the substrates type (linoleic acid and linolenic acid) and its concentration (0.10, 0.25, 0.50, 1.00, 1.50, 2.00 and 4.00 mM) as well as the concentration of enzyme extract (0.50, 1.00, 1.50, 2.00, 2.50 and 3.00%). The activity of LOX was monitored by absorbance increase at 234 nm during 240 s, expressed in millimolar per second per gram (mM/sg). Both fatty acids studied showed peak LOX activity: at pH 6.50 and substrate concentration of 1.5 mM. Experimental data obtained by Michaelis-Menten equation and Lineawer-Burk linearization presented Michaelis-Menten constant (KM) and the maximum velocity of enzyme (VMAX) values ranged from: 0.164 to 0.169 mM and 0.083 to 0.093 mM/sg, respectively. Linoleic acid proved to be the best substrate for the enzyme, and was used to determine the LOX activity considering the enzyme concentration. The most active enzyme concentration was 3.00%.