Influence of molting and starvation on the synthesis of proteolytic enzymes in the midgut gland of the white shrimp Penaeus vannamei

We investigated the effect of starvation as a stimulant of the digestive system on digestive proteinase activities in the white shrimp Penaeus vannamei. The starved organisms were sampled periodically according to the molting stage and compared with a continuously fed group. Molting stage was included as an independent variable. Most analyzed variables, except for trypsin, were more affected by starvation than by molting, indicating that starvation is a stimulant that masks the effect of molting and showing that food or alimentary stress is more conspicuous than physiological ones. We found that starvation is a stimulant that surpasses the effect of molting, and because it affects the activity of digestive proteinases, studies of starving organisms in combination with tools of molecular biology, can be a helpful working model in the understanding of mechanisms of regulation of digestive enzyme activity. In the starved organisms, trypsin and chymotrypsin activities were similar, suggesting dependence of one to the other. Changes in proteolytic activities and the number of protein bands in electrophoresis showed evidence of synthesis regulation in the midgut gland of white shrimp.     

Usage of energy reserves in crustaceans during starvation: status and future directions

In this paper, we review the current knowledge about the usage of carbohydrates, lipids and proteins as energy source by marine crustaceans during starvation. Crustaceans are a large and diverse group including some economically important species. The efforts to culture them for human consumption has prompted the interest to understand the preferences of energy sources to be applied for feed formulation and cost reduction. Important differences have been found among species and appear to be related not only to the biochemistry and physiology of nutrition, but also to the living environment of the crustaceans. Furthermore, crustaceans undergo morphological, physiological and behavioral changes due to their natural growing process that affect their feeding habits, an aspect that should be carefully considered. We discuss the current information on marine crustaceans about energy usage and describe areas of future research, where starvation studies render important insights.     

Invertebrate trypsins: a review

Food protein hydrolysis, a crucial step in digestion, is catalyzed by trypsin enzymes from the digestive apparatus of invertebrates. Trypsin appeared early in evolution and occurs in all phyla and, in the digestive systems of invertebrates, it became the most abundant proteinase. As in vertebrates, invertebrate trypsin is also present in several forms (isoenzymes). Its physiological importance in food protein digestion in several invertebrate species has emerged with compelling evidence; and several other physiological functions, such as regulation of digestive functions, are now settled. Recent advances in the knowledge of invertebrate trypsin synthesis, regulation, genetics, catalytic characteristics; structure, evolution, as well as inhibition, especially in non-Drosophilidae insects and in some crustaceans are reviewed. Most of the existing information is largely based on the use of several tools, including molecular techniques, to answer many still open questions and solve medical, agricultural, and food quality problems.     

Proteasome properties of hemocytes differ between the whiteleg shrimp <Emphasis Type="Italic">Penaeus vannamei</Emphasis> and the brown shrimp <Emphasis Type="Italic">Crangon crangon</Emphasis> (Crustacea,Decapoda)

Crustaceans are intensively farmed in aquaculture facilities where they are vulnerable to parasites, bacteria, or viruses, often severely compromising the rearing success. The ubiquitin-proteasome system (UPS) is crucial for the maintenance of cellular integrity. Analogous to higher vertebrates, the UPS of crustaceans may also play an important role in stress resistance and pathogen defense. We studied the general properties of the proteasome system in the hemocytes of the whiteleg shrimp, Penaeus vannamei, and the European brown shrimp Crangon crangon. The 20S proteasome was the predominant proteasome population in the hemocytes of both species. The specific activities of the trypsin-like (Try-like), chymotrypsin-like (Chy-like), and caspase-like (Cas-like) enzymes of the shrimp proteasome differed between species. P. vannamei exhibited a higher ratio of Try-like to Chy-like activities and Cas-like to Chy-like activities than C. crangon. Notably, the Chy-like activity of P. vannamei showed substrate or product inhibition at concentrations of more than 25 mmol L^?1. The K _M values ranged from 0.072 mmol L^?1 for the Try-like activity of P. vannamei to 0.309 mmol L^?1 for the Cas-like activity of C. crangon. Inhibition of the proteasome of P. vannamei by proteasome inhibitors was stronger than in C. crangon. The pH profiles were similar in both species. The Try-like, Chy-like, and Cas-like sites showed the highest activities between pH 7.5 and 8.5. The proteasomes of both species were sensitive against repeated freezing and thawing losing ~80–90% of activity. This study forms the basis for future investigations on the shrimp response against infectious diseases, and the role of the UPS therein.     

Protective Effect of Lacticaseibacillus casei CRL 431 Postbiotics on Mitochondrial Function and Oxidative Status in Rats with Aflatoxin B1–Induced Oxidative Stress

Probiotics and Antimicrobial Proteins - Studies have shown that the intracellular content of probiotic (postbiotics) has antioxidant properties, which can improve the antioxidant status in vivo....     

Responses to temperature and salinity by White Mullet Mugil curema: Possible explanation for the population decrease in Baja California Sur

The white mullet Mugil curema is distributed along the Gulf of Mexico and Pacific coasts and constitutes an important food resource in Mexico. However, during recent years the capture of this mugilid has decreased considerably, especially in Bahía and Ensenada de La Paz, Baja California Sur, Mexico. The effects of different levels of temperature (22, 26, and 30°C) and salinity (15, 25, and 35) on the instantaneous growth rate, energy content, and condition factor of early juveniles of Mugil curema were evaluated. Fish showed a lower growth rate, lower body energy content, and a less condition factor when exposed to high salinity and temperature. On the basis to the results obtained and considering the unusual extreme temperatures and salinity registered in Ensenada de La Paz, it is expected low functional performance of juvenile mullets beyond the overfishing might contribute to the population decrease of this resource.