Characterization of Trimethylamin-N-Oxide Demethylase (TMAOase) of Lizardfish from Indonesian Waters

Abstract

Formation of formaldehyde in fish can occur naturally through the breakdown of trimethylamine oxide (TMAO) become formaldehyde and the dimethylamine by-product in the fish during the postmortem phase by trimethylamine-N-oxide demethylase (TMAOase). The objective of this study was to characterize TMAOase which isolated from Saurida tumbil. The study was carried out by homogenizing of fish muscle using Tris-acetate buffer (pH 7.0) and centrifuged 10,000xg for 30 minutes. The supernatant was then added 1 M NaCl up to pH 4.5 and centrifuged at again. The supernatant was neutralized and heated at 80°C for 20 minutes, then centrifuged at 10,000xg for 30 minutes and then characterized by temperature, pH, cofactor effect on enzyme activity, and molecular weight. The same supernatant and then was dialyzed for 2 hours and determined its enzyme activity, protein concentration, and molecular weight. The result showed that TMAOase enzyme had optimum activity at pH 7 and temperature at 50°C and cofactor combination of cysteine, ascorbate, and FeCl2 could increase TMAOase activity. The dialysate had yield 3.71%, 1.78 fold purification, and molecular weight 20 kDa.