title: Funastrain c II: a cysteine endopeptidase purified from the latex of Funastrum clausum.
abstract: A cysteine endopeptidase, named funastrain c II, was isolated and characterized from the latex of Funastrum clausum (Asclepiadaceae). The molecular mass (mass spectrometry) of the protease was 23.636 kDa. The analysis of funastrain c II by SDS-PAGE revealed a single polypeptide chain. The enzyme showed a remarkable stability of its caseinolytic activity after incubation at temperatures as high as 70 degrees C. Inhibition and activation assays indicated the cysteinic nature of the funastrain c II catalytic site. The optimum pH of funastrain c II enzymatic activity varied according to the substrate used (9.0-10.0 for casein and 6.2-6.8 for PFLNA). Kinetic parameters were determined for N-alpha-CBZ-Ala p-nitrophenyl ester (Km = 0.0243 mM, kcat = 1.5 s(-1)) and L-pyroglutamyl-L-phenylalanyl-L-leucine-p-nitroanilide (PFLNA; KM = 0.1011 mM, kcat = 0.9 s(-1)). The N-terminal sequence of funastrain c II showed considerable similarity to other proteases isolated from latex of different Asclepiadaceae species as well as to other cysteine proteinases belonging to the papain family.
authors.affiliation: Laboratorio de Investigación de Proteínas Vegetales, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 711, B1900AVW, La Plata, Argentina. morcelle@biol.unlp.edu.ar
authors.forename: Susana R
authors.initials: SR
authors.lastname: Morcelle
authors.forename: Sebastián A
authors.initials: SA
authors.lastname: Trejo
authors.forename: Francesc
authors.initials: F
authors.lastname: Canals
authors.forename: Francesc X
authors.initials: FX
authors.lastname: Avilés
authors.forename: Nora S
authors.initials: NS
authors.lastname: Priolo
mesh_terms: D029062:Apocynaceae / Q000201:enzymology*; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007840:Latex / Q000737:chemistry / Q000378:metabolism*; D013058:Mass Spectrometry; D013997:Time Factors
chemical_list: D007840:Latex; D003546:Cysteine Endopeptidases