Abstract

Thiamine (vitamin B1) is a co-factor for enzymes involved in the TCA cycle and pentose-phosphate pathways. As an essential vitamin, it must be obtained through the diet. Thiamine deficiency can occur due to limited intake, poor bioavailability, or degradation. In fish, this manifests as a loss of equilibrium, spiral swimming patterns, hyperexcitability, and lethargy, and can result in early mortality syndrome. Thiaminase I is an enzyme found in select bacteria, plants, and fish that degrades thiamine in the presence of certain nucleophilic co-substrates. The consumption of prey fish containing this enzyme is believed to be responsible for thiamine deficiency and predator fish declines. Monitoring thiamine levels is critical for fisheries, necessitating a more cost-effective and easier method. A microplate enzymatic digestion method was developed for fish tissues reliant on dual-specificity: specificity of the thiaminase I enzyme towards thiamine and the specific fluorescence wavelengths of thiochrome, the oxidation product of thiamine.