Two New Cysteine Endopeptidases Obtained from the Latex of Araujia hortorum Fruits

W. OBREGÓN; MA. C. ARRIBÉRE,; S. MORCELLE DEL VALLE; C. LIGGIERI; N. CAFFINI; NORA PRIOLO

JOURNAL OF PROTEIN CHEMISTRY

Kluwer Academic Publishers.

Año: 2001 vol. 20 p. 317 - 325

0277-8033

Two new endopeptidases (araujiain h II and araujiain h III) were purified to homogeneity from the latex of Araujia hortorum fruits by a simple purification procedure involving ultracentrifugation and ion exchange chromatography. The enzymes have molecular weights of 23 718 and 23 545 (mass spectrometry), respectively. Isoelectric point of araujiain h II is 8.9, whereas araujiain h III has a pI higher than 9.3. The proteolytic activity assayed on caseine was maximum in the pH range of 8.0-9.0 for both endopeptidases. Inhibition assays were carried out with iodoacetate and E-64: the proteases were irreversibly inhibited, suggesting they belong to the cysteine proteases family. Esterolytic activity was determined on N-a-CBZ-amino acid-p-nitrophenyl esters. The highest kcat/Km values for the two enzymes were obtained with the glutamine derivative. The N-terminal sequences of araujiain h II and araujiain h III, showed a high percentage of homology with other plant cystein proteinases.