Obtainment and characterization of digestive aspartic proteases from the fish Caranx hippos (Linnaeus, 1766)

Obtenção e caracterização de proteases aspárticas digestórias do peixe Caranx hippos (Linnaeus, 1766)

Abstract

This work aimed to obtain aspartic proteases of industrial and biotechnological interest from the stomach of the crevalle jack fish (Caranx hippos). In order to do so, a crude extract (CE) of the stomach was obtained and subjected to a partial purification by salting-out, which resulted in the enzyme extract (EE) obtainment. EE proteases were characterized physicochemically and by means of zymogram. In addition, the effect of chemical agents on their activity was also assessed. By means of salting-out it was possible to obtain a purification of 1.6 times with a yield of 49.4%. Two acid proteases present in the EE were observed in zymogram. The optimum temperature and thermal stability for EE acidic proteases were 55 ºC and 45 °C, respectively. The optimum pH and pH stability found for these enzymes were pH 1.5 and 7.0, respectively. Total inhibition of EE acid proteolytic activity was observed in the presence of pepstatin A. dithiothreitol (DTT) and Ca²⁺ did not promote a significant effect on enzyme activity. In the presence of heavy metals, such as Al³⁺, Cd²⁺ and Hg²⁺, EE acidic proteases showed more than 70% of their enzymatic activity. The results show that it is possible to obtain, from the stomach of C. hippos, aspartic proteases with high proteolytic activity and characteristics that demonstrate potential for industrial and biotechnological applications.

Keywords:
waste recovery; fish enzymes; marine fish; aspartic proteases