title: Binding of the Kunitz-type trypsin inhibitor DE-3 from Erythrina caffra seeds to serine proteinases: a comparative study.
abstract: The effect of pH and temperature on kinetic and thermodynamic parameters (i.e., k(on),k(off),Ka,delta G0, delta H0 and delta S0 values) for the binding of the Kunitz-type trypsin inhibitor DE-3 from Erythrina caffra seeds (ETI) to bovine beta-trypsin, bovine alpha-chymotrypsin, the human tissue plasminogen activator, human alpha-, beta- and gamma-thrombin, as well as the M(r) 33,000 and M(r) 54,000 species of the human urinary plasminogen activator (also named urokinase) has been investigated. At pH 8.0 and 21.0 degrees C: (i) values of the second-order rate constant (K(on)) for the proteinase:ETI complex formation vary between 8.7 x 10(5) and 1.4 x 10(7)/M/s; (ii) values of the dissociation rate constant (k(off)) for the proteinase: ETI complex destabilization range from 3.7 x 10(-5) to 1.4 x 10(-1)/s; and (iii) values of the association equilibrium constant (Ka) for the proteinase:ETI complexation change from < 1.0 x 10(4) to 3.8 x 10(11)/M. Thus, differences in k(off) values account mostly for the large changes in Ka values for ETI binding. The affinity of ETI for the serine proteinases considered can be arranged as follows: bovine beta-trypsin > human tissue plasminogen activator > bovine alpha-chymotrypsin >> human alpha-, beta- and gamma-thrombin approximately M(r) 33,000 and M(r) 54,000 species of the human urinary plasminogen activator. Moreover, the serine proteinase:ETI complex formation is an endothermic, entropy-driven, process.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Blackett Laboratory, Imperial College, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Onesti
authors.forename: D J
authors.initials: DJ
authors.lastname: Matthews
authors.forename: P
authors.initials: P
authors.lastname: Aducci
authors.forename: G
authors.initials: G
authors.lastname: Amiconi
authors.forename: M
authors.initials: M
authors.lastname: Bolognesi
authors.forename: E
authors.initials: E
authors.lastname: Menegatti
authors.forename: P
authors.initials: P
authors.lastname: Ascenzi
mesh_terms: D000595:Amino Acid Sequence; D003198:Computer Simulation; D004895:Erythrina / Q000201:enzymology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010946:Plants, Medicinal; D011485:Protein Binding; D012639:Seeds / Q000201:enzymology; D013816:Thermodynamics; D014360:Trypsin Inhibitor, Kunitz Soybean / Q000378:metabolism*
chemical_list: D014360:Trypsin Inhibitor, Kunitz Soybean