Partial characterization of digestive proteases in juveniles of Microphis brachyurus (short-tailed pipefish) (Syngnathiformes: Syngnathidae)

Leonardo Martínez-Cárdenas,Carlos A Frías-Quintana,Jesús T Ponce-Palafox,Oscar U Hernández-Almeida,Luis D Jiménez-Martínez,Javier Bello-Pineda,Carlos A Álvarez-González,Leonardo U Arellano-Méndez,Rafael Martínez-García

doi:10.1590/1982-0224-2019-0085

Abstract

ABSTRACT Short-tailed pipe fish (Microphis brachyurus) is a freshwater organism with high economic potential for the aquarium hobby, so it is necessary to implement methods to promote its culture through studies of digestive physiology. General activities of acid and alkaline proteases were evaluated, as well as the effect of pH, temperature and inhibitors. The optimal pH of stomach proteases was 2, while the optimal pH of intestinal proteases was 10. Optimal temperature for the acidic proteases was 35 ºC, while for alkaline proteases it was 45 ºC. Thermal stability showed high resistance at 35 ºC for both acid and alkaline proteases (above 100% residual activity). Acid proteases are resistant at pH 2 (50% of residual activity), meanwhile alkaline proteases were highly resistant at pH 10 (90% of residual activity). Acid proteases were inhibited by 80% with pepstatin A and alkaline proteases were inhibited with TLCK and TPCK for trypsin (75%) and chymotrypsin (80%), respectively. Finally, metallo-proteases were 75% partially inhibited some serine proteases by 75% with EDTA. In conclusion, M. brachyurus has a good digestive capacity, since they can degrade a wide variety of proteins due to their greater proteolytic activity.

Highlights

The short-tailed pipefish, Microphis brachyurus (Bleeker, 1854), is a subtropical estuarine fish, distributed along the Gulf of Mexico
The results obtained in the enzymatic characterization of juveniles of short-tailed pipefish (Microphis brachyurus) showed that this species exhibits a relatively high activity of alkaline digestive proteases compared with other fish species such as Scleropages formosus (Müller, Schlegel, 1840) (Natalia et al, 2004), turbot Scophthalmus maximus (Linnaeus, 1758) (Wang et al, 2006), Mayan cichlid Cichlasoma uropthalmus (CuencaSoria et al, 2014), Cichlasoma trimaculatum (=Amphilophus trimaculatus) (Toledo-Solís et al, 2017), and Cichlasoma beani (=Mayaheros beani) (Mártinez-Cárdenas et al, 2017)
The latter two species have carnivorous habits characterized by high acid protease activities (>1500 Unit Enzymatic Activity (UEA) mg of protein-1) in the stomach, which is the most important organ for the acid digestion of proteins, as well as a lower alkaline digestive activity in the intestine (

Summary

Introduction

The short-tailed pipefish, Microphis brachyurus (Bleeker, 1854), is a subtropical estuarine fish, distributed along the Gulf of Mexico. It belongs to the Syngnathidae family, which includes sea dragons, seahorses, and pipefish. Natural populations of M. brachyurus are affected in Mexico by unregulated fishing as this species is traded as an aquarium fish without formal records as occurs with other syngnathid species around the world (Rosa et al, 2011). 37 species of pipefish have been reported to inhabit both freshwater and saltwater systems (Nelson et al, 2016), including M. brachyurus, which often faces inadequate culture practices in the average home aquarium as it is maintained in tanks with conventional freshwater tropical fish

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