Abstract
<p class="1Body">Common snook (<em>Centropomus undecimalis</em>) is a marine species with high aquaculture potential; although its digestive physiology is still unknown and knowledge of that could allow the development of a balanced feed for commercial culture of this fish. The objective of this study was to partially characterize the digestive proteases in <em>C. undecimalis</em> using electrophoretic and biochemical techniques. A total of 50 wild snook juveniles were used to determine the optimal values of pH stability and temperature as well as the effect of inhibitors on digestive, gastric and intestinal proteases. The optimal pH for gastric proteases was obtained to be 2 with stability obtained between 2 and 8; the optimal temperature was detected at 75ºC for in vitro test, and the thermal stability was between 25 and 45ºC. Intestinal proteases showed two peaks of activity at a pH of 7 and 11; meanwhile, the greatest stability was found between a pH of 4 and 10; the optimal temperature was at 65ºC, and the greatest stability was detected between 35 and 45ºC. Up to 86% of the gastric protease activity was inhibited by pepstatin A; meanwhile, the intestinal proteases TPCK, TLCK, 1-10 Phenanthroline, SBT1, EDTA, PMSF and ovalbumin reduced the activity by 17%, 68%, 85%, 41%, 40.5%, 60% and 59%, respectively.</p>
Highlights
The nutrient requirement in a fish species varies depending on several factors and it is determined by the quantity and quality of macronutrients and micronutrients (Fenerci, & Sener, 2005)
The optimal pH for gastric proteases was obtained at a pH of 2
The optimal temperature of the acidic proteases was shown at 75 oC, decreasing at 85 oC (Figure 1c); the optimal activity of the alkaline proteases was registered at 65 oC; they showed high activity from 45 oC until a drastic fall at 75 oC (Figure 1d)
Summary
The nutrient requirement in a fish species varies depending on several factors and it is determined by the quantity and quality of macronutrients (proteins, lipids and carbohydrates) and micronutrients (vitamins and minerals) (Fenerci, & Sener, 2005). Considering the above, the secretion of digestive enzymes depends on the physicochemical characteristics of the internal environmental, the quality and quantity of nutrients, and the presence of inhibitors in the feed (Lazo, Mendoza, Holt, Aguilera, & Arnold, 2007; Murashita et al 2015). In this sense, the studies on protease characterization allow us to understand the capacity of fish to hydrolyze and metabolize proteins, which are necessary for adequate growth and development (Ma et al 2005).
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