Amino acid sequence and disulphide-bridge pattern of three g-thionins from Sorghum bicolor

The complete primary structure of a new a-amylase inhibitor from Sorghum bicolor belonging to the y-thionin family has been determined and the amino acid sequences of two components of the family already elucidated have been corrected by combining the classical Edman degradation with advanced mass spectrometric procedures. The same integrated approach allowed us to define the pattern of the disulphide bridges in the three isoinhibitors. The arrangement of the cysteine pairing was determined as Cys3-Cys47, Cys14-Cys34, Cys20-Cys41 and Cys24-Cys43. The amino acid sequences of the a-amylase inhibitors share a high degree of similarity with the related plant y-thionins. All these proteins consist of 47 residues, contain eight cysteine residues forming four disulphide bridges, and show the presence of two clusters of basic amino acids located at both ends of the polypeptide chain. The pattern of S-S bridges determined for the isoinhibitors is identical to that inferred by NMR analysis in two related y-thionins, thus suggesting a highly conserved organization of the disulphide pairing. These results indicate that the structural similarities among the different y-thionins extend far beyond the primary structure and possibly concern the secondary structure and the general folding of the entire y-thionin family

Efeitos farmacológicos da suplementação dietética com arginina em ratos com tumor sólido de Walker 256

Os efeitos da suplementação com arginina na dieta de portadores de câncer são controversos. O objetivo deste trabalho é avaliar os efeitos da suplementação dietética com arginina no cresciemnto tumoral, disserninação metastática, metabolismo de aminoácidos, alterações hematológicas, tempo de sobrevida e peso corporal de ratos Wistar com tumor sólido de Walker 256. Foram administradas soluções por via gástrica, contendo arginina nas concentrações de 4%, 6% e dieta padrão (controle). A suplementação com arginina inibiu a disseminação de células tumorais no modelo experimental, embora o crescimento tumoral não tenha sido afetado significantemente. O tempo de sobrevida dos animais com tumor sólido não foi afetado de forma significativa. Foi observado diminuição significativa do peso corpóreo após a administração da arginina a 6% (pPharmacological effects of arginine supplementation in rats with Walker 256 solid tumor. The effects of diet arginine supplementation for those with cancer are controversial. We evaluate the effects of dietetic supplementation with arginine over body weight, growth of tumor, metastatic dissemination, surviving time, amino acid metabolism, haematological changes of the rats with Walker 256 solid tumor. Intragastrical solutions with arginine at 4% and 6%, a standard diet (control) were administered to the animals. The supplementation with arginine was associated with a lower weight gain during the study period (p<0.05). Surviving time of the rats with solid tumor did not vary significantly between the groups. The rate of metastase was lower in animals with Walker 256 solid tumor supplemented with arginine. The amino acid metabolism was estimulate in the animals after arginin supplementation at 4% and 6%, demonstrated by significant increases in blood levels of arginine, ornitine, citruline, proline and histidin when compared to the control group. Anaemia was less severe in the rats with Walker 256 solid tumor that received arginine supplementation. The results suggest that arginine 6% supplementation may have pharmacologic effect in rats with Walker 256 solid beyon the nutritional one

BTCI enhances guanylin-induced natriuresis and promotes renal glomerular and tubular effects

Guanylin and uroguanylin are small cysteine-rich peptides involved in the regulation of fluid and electrolyte homeostasis through binding and activation of guanylyl cyclases signaling molecules expressed in intestine and kidney. Guanylin is less potent than uroguanylin as a natriuretic agent and is degraded in vitro by chymotrypsin due to unique structural features in the bioactive moiety of the peptide. Thus, the aim of this study was to verify whether or not guanylin is degraded by chymotrypsin-like proteases present in the kidney brush-border membranes. The isolated perfused rat kidney assay was used in this regard. Guanylin (0.2 µM) induced no changes in kidney function. However, when pretreated by the black-eyed pea trypsin and chymotrypsin inhibitor (BTCI - 1.0 µM; guanylin - 0.2 µM) it promoted increases in urine flow (deltaUF of 0.25 &plusmn; 0.09 mL.g-1/min, P < 0.05) and Na+ excretion (% delta ENa+ of 18.20 &plusmn; 2.17, P < 0.05). BTCI (1.0 µM) also increased %ENa+ (from 22.8 &plusmn; 1.30 to 34.4 &plusmn; 3.48, P < 0.05, 90 minutes). Furthermore, BTCI (3.0 µM) induced increases in glomerular filtration rate (GFR; from 0.96 &plusmn; 0.02 to 1.28 0.02 mL.g-1/min, P < 0.05, 60 minutes). The present paper strongly suggests that chymotrypsin-like proteases play a role in renal metabolism of guanylin and describes for the first time renal effects induced by a member of the Bowman-Birk family of protease inhibitors