Partial characterization of digestive proteases in sheepshead, Archosargus probatocephalus (Spariformes: Sparidae)

María L Merino-Contreras,María L Jiménez-Badillo,Carlos A Álvarez-González,Emyr S Peña-Marín,Froylán Sánchez-Morales

doi:10.1590/1982-0224-20180020

Abstract

ABSTRACT Digestive proteases were partially characterized in sheepshead juveniles, using biochemical and electrophoretic techniques. Results showed higher activity level of the stomach proteases (2.39 ± 0.02 U mg protein-1) compared to the intestinal proteases (1.6 ± 0.1 U mg protein-1). The activity of trypsin, chymotrypsin, leucine aminopeptidase and carboxypeptidase A was also recorded. The optimum temperature of the stomach proteases was recorded at 45 °C, while for intestinal proteases was recorded at 55 °C. Stomach proteases showed less stability to temperature changes than intestinal proteases. An optimum pH of 2 was recorded for stomach proteases with high stability under acidic conditions, while an optimum pH of 9 was recorded for intestinal proteases showing high stability under alkaline conditions. Stomach proteases were inhibited around 78% with Pepstatin A, indicating the presence of pepsin as the main protease. The stomach proteases zymogam revealed one active band with Rf of 0.49, this enzyme was completely inhibited by Pepstatin A. The intestinal proteases zymogram revealed four active proteases (51.3, 34.9, 27.8 and 21.2 kDa) that were inhibited by TLCK, which mainly represent a trypsin-like serine proteases. It can be conclude that digestion in sheepshead can be considered as a carnivorous species with an omnivorous tendency.

Highlights

The sheepshead fish, Archosargus probatocephalus (Walbaum, 1792), is a coastal, subtropical marine fish that regularly enters brackish waters
For alkaline protease activity the optimum pH was observed to be 9 (Fig. 1c), while greater stability to changes in pH was observed at pH 10, demonstrating a significant difference (P
The stability of acid proteases was reduced to 90% at temperatures of 55 and 65 °C after 30 minutes of preincubation (Fig. 2b)

Summary

Introduction

The sheepshead fish, Archosargus probatocephalus (Walbaum, 1792), is a coastal, subtropical marine fish that regularly enters brackish waters. This species is an important component of the commercial and recreational-sport fisheries along the Atlantic coast of the US and the Gulf of Mexico (Figueira, Coleman, 2010; McDonough et al, 2011), and has recently been considered viable for the development of mariculture in the southeast Mexican region (RNIIPA, 2012). Tucker (1998, 2004) describes the species with aquaculture potential since it has great adaptability to captivity, a wide range of feeding sources, adapts to high density conditions and has been induced to spawn, allowing the production of juveniles under laboratory conditions. Juvenile sheepsheads have been previously reported to develop carnivorous habits when they grow to a length of around 50 mm (GSMFC, 2006), whilst the adults are considered omnivorous since they mainly feed on algae and invertebrates (Jobling, 1995; Cutwa, Turingan, 2000; Castillo-Rivera et al, 2007)

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