Philibertain g I, the Most Basic Cysteine Endopeptidase Purified from the Latex of Philibertia gilliesii Hook. et Arn. (Apocynaceae).

C. SEQUEIROS; M.J. TORRES ; S.A. TREJO ; J. L. ESTEVES ; C. L. NATALUCCI; L. M. I. LÓPEZ

JOURNAL OF PROTEIN CHEMISTRY

Springer

Lugar: Netherlands; Año: 2005 vol. 24 p. 445 - 453

0277-8033

A new papain-like cysteine peptidase isolated from latex of Philibertia gilliesii  Hook. et Arn., Apocynaceae (formerly Asclepiadaceae) has been purified and characterized. The enzyme, named philibertain g I, is the most basic component present in latex extracts and was purified by acetone fractionation followed by cation exchange chromatography (SP-Sepharose HR) using FPLC system. Homogeneity was confirmed by SDS-PAGE and mass spectroscopy (MS). Molecular mass of the enzyme was 23,530 Da (MALDI-TOF MS), its isoelectric point was >10.25, and maximum proteolytic activity (casein) was achieved at pH 7–8. The new protease was inhibited by E-64 a cysteine peptidases inhibitor. Km was 0.15 mM, using PFLNA as substrate. The N-terminal sequence of philibertain g I (LPASVDWRKEGAVLPIRHQGQCG) was compared with those of twenty plant proteases. Philibertain g I showed the higher degree of identity (73%) with caricain, one of the Carica papaya endopepetidases.