Enzimas de organismos aquÃticos e suas aplicaÃÃes fisiolÃgicas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

In the last years, there has been a general increase in human demand for fishery products, followed by a significant increase in the world production of aquatic organisms. The growth of fishery industry generates, as consequence, large amounts of wastes and by-products rich in biomolecules, which are discharged into envioronment. Fishery wastes can be used in several physiological studies related to digestive physiology of marketable aquatic species and to the develolpment of alternative ingredients which can be used as component of animal feeds. The aim of the present work was to investigate digestive enzymes from the hepatopancreas of some peneaid shrimps and evaluate the effects of diets with different shrimp protein hydrolysate (SPH) concentrations on growth, body composition and digestive physiology of Oreochromis niloticus juveniles. Amylases from the hepatopancreas of Farfantepenaeus subtilis (13g), Litopenaeus schmitti (23g) and L. vannamei (11 and 25g) and proteases from F. subtilis (6 and 13g) and F. paulensis (8g) were characterized according the following properties: optima pH and temperature, thermal stability, effect of inhibitors and metalic ions, electrophoresis and zymograms. Amylases from all species presented residual activity above 85% at alkaline pH (7.0 â 8.0) and at 40 â 50oC and were not thermostable at temperatures greater than 55oC. Amylases of all species were activated by calcium chloride at 1mM but were inhibited at 5 and 10mM. All other ions employed showed inhibitory effect at any employed concentration. A strong inhibition of alpha-amylase Type I inhibitor on enzyme activity was observed for F. subtilis and L. schmitti, but the same result was not observed for L. vannamei. The substrate SDS-PAGE zymograms revealed nine isoforms of amylase for F. subtilis, eight for L. schmitti and seven and ten for L. vannamei of 11 and 25g, respectively. Trypsin, chymotripsyn and leucine-aminopeptidase activity was detected for F. subtilis and F. paulensis. The greatest activity of all proteinases also occurred at alkaline pH (pH 7.5 â 9.0) and temperature from 45 to 55 oC. The substrate SDS-PAGE zymograms revealed eight proteinase bands for F. paulensis and six ones for F. subtilis. Aminopeptidase activity (Arg, Leu, Lys, Phe, Val) and recommended concentrations of these essential amino acids in penaeid shrimp diets were positively correlated (p<0.05). The effects of different dietary inclusion levels of shrimp protein hydrolysate (SPH) on digestive enzyme activity of Nile tilapia juveniles were evaluated and correlated with growth parameters and body composition. SPH was included in diets at concentrations of 0, 1.5, 3 and 6%. A commercial diet was used as reference. Hemoglobin, azocasein, BApNA, SApNA, AA-β naphytilamide and starch were used as substrates. Despite some differences, there was no correlation between enzyme activity and different SPH concentrations in the diets. Substrate- SDS-PAGE zymogram was also performed for the analysis of changes in the profile of Nile tilapia digestive proteases caused by the inclusion of protein hydrolysate. Zymograms revealed 12 proteolytic bands, eight of which responded to incorporation of SPH. Inhibition zymograms indicated that there was a decrease in the activity of three enzymes with trypsin activity as SPH increases, whereas the opposite occurred for one aminopeptidase. Distinct protease profiles were also found for each treatment, suggesting adaptability of the Nile tilapia to the different diets. Trypsin and aminopeptidase activity was positively correlated with growth parameters and carcass protein content and negatively correlated with feed conversion ratio and carcass lipid content. Since digestion involves the joint action of different enzymes, adequate comprehension of enzyme characteristics is required for the assessment of the digestive capability of the different species. Enzyme studies may provide basic information useful for further nutritional researches, as well as be an efficient tool for analysis of different diets

ASSUNTO(S)

fisiologia digestiva shrimps nile tilapia tilÃpia do nilo feeds enzimas digestivas hidrolisado protÃico de camarÃes digestive physiology ciencias biologicas camarÃes marinhos shrimp protein hydolysate digestive enzymes fisiologia digestiva

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