Vibrio parahaemolyticus inativado por calor pode modular a atividade de fenoloxidases no hepatopâncreas do camarão Litopenaeus vannamei

Abstract

Carciniculture has grown in recent years, especially in Brazil for the shrimp Litopenaeus vannamei. However, infectious diseases represent a major threat to productivity, such as the disease caused by Vibrio parahaemolyticus, which is responsible for high mortality rates. Thus, some alternatives have been taken to understand the innate immunity in shrimp, such as the system prophenoloxidase (proPO) that detects the activity of phenoloxidases in the hepatopancreas of shrimp, whose modulation is carried out by pathogens. Therefore, the present study aims to analyze the effect of inactivated V. parahaemolyticus on the L. vannamei hepatopancreas phenoloxidase enzymes and to observe whether the activity of these enzymes can be modulated through a second challenge with activated V. parahaemolyticus. The effect of inactivated pathogen followed by live bacteria in the phenoloxidase enzymes were evaluated in crude hepatopancreas extracts, in these treatments (without V. parahaemolyticus inactivated, with V. parahaemolyticus inactivated, with V. parahaemolyticus alive, with V. parahaemolyticus inactivated by heat and V. parahaemolyticus live). The activities were measured by incubating the crude extracts with L-dopa (non-specific substrate) and Hydroquinone (specific substrate of laccase phenoloxidase enzymes) and tyrosinase phenoloxidase inhibitor (13 mg / mL tropolone). Then the effect of temperature (25 ° C - 85 ° C) on the activity of phenoloxidases was tested. The enzymatic activity of the inactivated Vibrio group followed by infection with live Vibrio was not significant in relation to the live Vibrio group, just as there was a negative activity modulation in the live vibrio group, determining that it decreases the activity to establish itself in the shrimp. In addition, the activity was slightly inhibited (32.3%) by tropolone and the residual activity showed that laccase enzymes may be present marjoritly in the hepatopancreas of L. vannamei. This indicates that most of the phenoloxidase enzymes are laccase and that few enzymes are tyrosinase and that live pathogen is able to decrease enzyme activity in order to settle in the shrimp and cause an infection. Therefore, it can be concluded that neither phenoloxidase-like enzymes activity was not modulated in hepatopancreas following inactivated V. parahaemolyticus nor these bacteria prevent the effects of the active pathogen in these enzymes