Articulo
Purification and Biochemical Characterization of Asclepain c I from the Latex of <i>Asclepias curassavica</i> L.
Registro en:
issn:1572-3887
Autor
Liggieri, Constanza Silvina
Arribére, María Cecilia
Trejo, Sebastián Alejandro
Canals, Francesc
Avilés, Francesc X.
Priolo de Lufrano, Nora Silvia
Institución
Resumen
In this work we report the isolation, purification and characterization of a new protease from latex of <i>Asclepias curassavica</i> L. Crude extract (CE) was obtained by gathering latex on 0.1M citric-phosphate buffer with EDTA and cysteine with subsequent ultracentrifugation. Proteolytic assays were made on casein or azocasein as substrates. Caseinolytic activity was completely inhibited by E-64. Stability at different temperatures, optimum pH and ionic strength were evaluated by measuring the residual caseinolytic activity at different times after the incubation. CE showed the highest caseinolytic activity at pH 8.5 in the presence of 12 mM cysteine. CE was purified by cation exchange chromatography (FPLC). Two active fractions, homogeneous by SDS-PAGE, were isolated. The major purified protease (asclepain cI) showed a molecular mass of 23.2 kDa by mass spectrometry and a pI higher than 9.3. The N-terminal sequence showed a high similarity with those of other plant cysteine proteinases. When assayed on N-α-CBZ-aminoacid-p-nitrophenyl esters, the enzyme showed higher preference for the glutamine derivative. Determinations of kinetic parameter (k<sub>m</sub> and K<sub>cat</sub>) were performed with PFLNA. Centro de Investigación de Proteínas Vegetales