No abstract

Disintegrins and disintegrins-like proteins are able to inhibit platelet aggregation and integrin-mediated cell adhesion. The aim of this study was to produce one disintegrin-like cloned from Bothrops leucurus venom gland and to characterize it regarding biological activity. The recombinant protein was purified by one step procedure involving anion-exchange chromatography (DEAE-cellulose) and presented a molecular mass of 10.4 kDa. The purified protein was able to inhibit platelet aggregation induced by collagen (IC₅₀ = 0.65 μM) and to inhibit growth of Ehrlich tumor implanted in mice by more than 50% after 7 days administration of 10 μg/day. No effects were observed upon adenosine 5'-diphosphate (ADP)-and arachidonic acid (AA)-induced platelet aggregation. The recombinant protein was recognized by an antibody specific for jararhagin one metalloproteinase isolated from Bothrops jararaca venom, and therefore it was named leucurogin. Anti-angiogenesis effect of leucurogin was evaluated by the sponge implant model. After 7 days administration leucurogin inhibited, in a dose dependent way, the vascularization process in the sponge. Leucurogin represents a new biotechnological tool to understand biological processes where disintegrins-like are involved and may help to characterize integrins that can be involved in development and progression of malignant cells.

The partition behaviour of cutinase on poly(ethylene glycol) (PEG)-hydroxypropyl starch aqueous two-phase systems was characterized. The effect of molecular mass of PEG, the pH of the system and tie-line length on cutinase partition coefficient and cutinase yield to the top phase was investigated for systems prepared with a purified hydroxypropyl starch (Reppal PES 100) and a crude one (HPS). The effect of the presence of different salts, such as sodium chloride, sodium sulphate and ammonium sulphate, on cutinase partition was also studied. The results lead to the conclusion that aqueous two-phase systems composed of PEG and hydroxypropyl starch are not efficient in the purification of cutinase. In the majority of cases, the partition coefficients were very close to 1, with pH being the factor which affects most cutinase partition. Partition coefficients were significantly improved when salts were added to the systems. For PEG 4000-Reppal PES 100 [at pH 4.0; 0.5 M (NH) SO ], the partition coefficient for cutinase was 3.7, while a value of 12 was obtained for PEG 4000-HPS (at 4 2 4 pH 4.0; 1 M NaCl). An isoelectric point (pI) of 7.8 was confirmed for cutinase by constructing a cross partition graphic from the results obtained in the experiments with different salts.

We studied the performance of Fusarium solani pisi cutinase, immobilized on a zeolite, in supercritical fluids. The catalytic activity of the enzyme was strongly dependent on water activity, was unaffected by pressure up to 300 bar, and was higher in supercritical ethylene than in supercritical carbon dioxide. The enzyme was very selective toward one of the isomers of 1-phenylethanol, with an enantiomeric excess of virtually 100%, regardless of water activity, pressure, solvent, and temperature. We used the X-ray crystal structure of the enzyme and did a computer modeling of the structures of the transition states formed by the two enantiomers. The differences between these structures helped elucidate the preference for the (R)-enantiomer.