A 38.5 kDa alkaline protease from pyloric caeca of tambaqui (Colossoma macropomumj, a tropical freshwater fish, was partially purified in three steps: thermal treatment (45Cfor 30 min), salting‐out (ammonium sulfate at 40–80% of saturation) and gel filtration (Sephadex G‐75), The purification and yield were 51.2‐fold and 40%, respectively. The effects of pH, temperature, inhibitors, and substrates on proteolytic activities of partially purified enzyme were investigated. The optimum pH was 9.5, while the optimum temperature was 60C. This alkaline proteolytic activity remained unaltered after 30 min incubation at 55C. Active site inhibition provided additional evidence that this activity is attributed to a trypsin‐like enzyme.

No abstract

The effects of pH, temperature, inhibitors, and substrates on proteolytic activities of crude extracts from the stomach, liver, pyloric caeca, and intestines of Colossoma macropomum were investigated. The highest acid and alkaline proteolytic activities were found in stomach and pyloric caeca, respectively. The optimum pH for the acid and alkaline proteases were 1.8 and 7.0–9.0, respectively, while the optimum temperatures were 35C and 65C. This alkaline protease thermal stability remained unaltered after 90 min incubation at 55C. A pepsin‐like protease was responsible for most of the acidic proteolytic activity (Pepstatin A inhibited approximately 90%), whereas PMSF inhibited about 40% of the alkaline protease. The alkaline proteolytic activity has attractive thermal properties for industrial applications.

The effect of different farming systems (cage, pond) upon digestive enzyme activities of Nile tilapia was evaluated. Juvenile Nile tilapia (87.61 ± 1.52 g) were simultaneously cultured in pond and cage systems during 90 days. Cages used nutritional biphasic plan (35 and 32 % crude protein-CP feeds) and ponds used nutritional triphasic plan (35, 32 and 28 % CP feeds). Biometric measurements were monthly performed for adjustments in feeding regimes and removal of intestine tissues to evaluate the performance of enzyme activities. Total proteolytic, amylase and lipase activities were not statistically different between the treatments throughout the periods analyzed (31, 63 and 94 days of culture). However, trypsin and chymotrypsin activities were higher with 31 and 63 days of culture in fish from pond system, suggesting that natural food may have influenced these activities. A positive correlation was observed between the recommended concentration of essential amino acids for Nile tilapia and specific aminopeptidases activity in fish cage system. Substrate-SDS-PAGE revealed 12 active proteolytic bands in both systems. However, integrated density (ID) values were higher in the bands of ponds. Specimens of either cage or pond exhibited five bands of amylolytic activity. Fish from cage and pond systems showed the highest values of ID within 31 days of cultivation. In this study, the complexity of digestive functions could be verified for animals maintained under commercial conditions. Some of the assessed enzymes may show adaptations of their activities and/or expression that allow the fish to achieve a more efficient nutrient assimilation.

The effect of different dietary concentrations of shrimp protein hydrolysate (SPH) on digestive enzyme activity of Nile tilapia juveniles was evaluated. SPH concentrations in diets were 0, 15, 30 and 60 g kg-1 (treatments SPH0, SPH15, SPH30 and SPH60, respectively). Hemoglobin, azocasein, BApNA (Na-benzoyl-DL-arginine-p-nitroanilide), SApNA (Suc-Ala-Ala-Pro-Phe p-nitroanilide), aminoacyl of b-naphthylamide and starch were used as substrates for enzyme activity determinations. The activity of total alkaline protease was significantly higher (P \ 0.05) in fish under SPH15 and SPH60 treatments than in the control (SPH0). However, the effect was not dosedependent. Substrate-SDS-PAGE was also performed to evaluate changes in the profile

No abstract

Obtaining corn hybrid seeds (Zea mays L.) with high vigour depends on the parental lines and the direction of the cross, and this relates to seed desiccation tolerance and composition. This research studied reciprocal crosses between pairs of proprietary, elite parent lines (L1 and L5; L2 and L4) producing hybrid seeds with different qualities attempting to correlate vigour with seed composition, focusing on storage proteins, starch and soluble sugar amounts. Four corn hybrid seed lots produced from reciprocal crosses were compared (HS 15 with HS 51, and HS 24 with HS 42) by assessing germination, vigour, and seedling emergence in the field. Seed composition was assessed in mature, dehydrated seeds. Proteins were extracted, quantified, and analysed by electrophoresis and densitometry. Starch amounts were assessed using a kit and soluble sugars were determined using high performance liquid chromatography with pulsed electrochemical detection. The L1 and L2 lineages, used as female parents, provided seeds with lower vigour; however, the quantification of major protein bands, and sucrose, raffinose and stachyose were similar between seed lot pairs. While both total seed protein and starch varied between reciprocal hybrids for one of the two sets of crosses, the amounts of neither correlated with seed vigour. Interestingly, hybrids with low seed vigour (HS 15, HS 24) accumulated greater amounts of fructose relative to their reciprocal; correlation analysis confirmed these results. We demonstrate different effects on seed vigour dependent on the maternal parent in reciprocal crosses producing hybrid corn seeds. We also show that vigour is negatively correlated with seed reducing sugar contents.

No abstract