title: Characterization of chymotrypsin-ι-carrageenan complex in aqueous solution: a solubility and thermodynamical stability study.
abstract: The aim of this study is to report the results of research work on the molecular mechanism of complex formation between chymotrypsin and a negatively charged natural strong polyelectrolyte, ι-carrageenan, using spectroscopy techniques. The carrageenan-chymotrypsin complex showed a maximal non-solubility at pH around 4.50 with a stoichiometric ratio between 8 and 33 g of chymotrypsin per g of carrageenan. These values were depended on the enzyme concentration, pH and ionic strength medium. The insoluble complex was redissolved by modifying the pH and by a NaCl concentration around 0.2 M in agreement with a coulombic mechanism of complex formation. The non-soluble complex formation showed biphasic kinetics. A fast step was carried out around 10 s and a coulombic mechanism takes place, and a slower step of around 120 s, where participate only Van der Waals forces. The enzymatic activity of chymotrypsin was maintained even in the presence of carrageenan (0.005%, w/v).
authors.affiliation: Laboratory of Physical Chemistry Applied to the Bioseparation, Faculty of Biochemical and Pharmaceutical Sciences, CONICET, National University of Rosario, Suipacha 570, S2002RLK Rosario, Argentina.
authors.forename: Nadia Woitovich
authors.initials: NW
authors.lastname: Valetti
authors.forename: Valeria
authors.initials: V
authors.lastname: Boeris
authors.forename: Guillermo
authors.initials: G
authors.lastname: Picó
mesh_terms: D002351:Carrageenan / Q000737:chemistry*; D002918:Chymotrypsin / Q000737:chemistry*; D004795:Enzyme Stability; D012995:Solubility; D013816:Thermodynamics
chemical_list: D002351:Carrageenan; D002918:Chymotrypsin