RESUMO
Two cysteine endopeptidases from latex of Araujia angustifolia (araujiain aI and araujiain aIII) were purified and characterized by means of conventional and proteomics techniques (MALDI-TOF). N-terminal sequences showed a high percentage of identity with cysteine proteinases belonging to the papain family. The peptide mass fingerprint analysis demonstrated a close homology among both proteinases.
Assuntos
Apocynaceae/enzimologia , Cisteína Proteases/química , Papaína/química , Mapeamento de Peptídeos/métodos , Proteínas de Plantas/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Biologia Computacional/métodos , Cisteína Proteases/isolamento & purificação , Cisteína Proteases/metabolismo , Inibidores de Cisteína Proteinase/química , Ésteres/metabolismo , Frutas/enzimologia , Concentração de Íons de Hidrogênio , Látex/química , Papaína/metabolismo , Proteínas de Plantas/antagonistas & inibidores , Proteínas de Plantas/isolamento & purificação , Proteínas de Plantas/metabolismoRESUMO
A new plant endopeptidase was obtained from unripe fruits of Bromelia balansae Mez (Bromeliaceae). Crude extracts were partially purified by ethanol fractionation. This preparation (redissolved ethanol precipitate, REP) showed maximum activity at pH 8.8-9.2, was very stable even at high ionic strength values (no appreciable decrease in proteolytic activity could be detected after 24 h in 1 M sodium chloride solution at 37 degrees C), and exhibited high thermal stability (inactivation required heating for 60 min at 75 degrees C). Anion exchange chromatography allowed the isolation of a fraction purified to mass spectroscopy, SDS-PAGE, and IEF homogeneity, named balansain I, with pI = 5.45 and molecular mass = 23192 (mass spectrometry). The purification factor is low (2.9-fold), but the yield is high (48.3%), a common occurrence in plant organs with high proteolytic activity, where proteases represent the bulk of protein content of crude extracts. Balansain I exhibits a similar but narrower pH profile than that obtained for REP, with a maximum pH value approximately 9.0 and was inhibited by E-64 and other cysteine peptidases inhibitors but not affected by inhibitors of the other catalytic types of peptidases. The alanine and glutamine derivatives of N-alpha-carbobenzoxy-L-amino acid p-nitrophenyl esters was strongly preferred by the enzyme. The N-terminal sequence of balansain I showed a very high homology (85-90%) with other known Bromeliaceae endopeptidases.