title: Binding of the recombinant proteinase inhibitor eglin c from leech Hirudo medicinalis to human leukocyte elastase, bovine alpha-chymotrypsin and subtilisin Carlsberg: thermodynamic study.
abstract: The effect of pH and temperature on the apparent association equilibrium constant (Ka) for the binding of the recombinant proteinase inhibitor eglin c from leech Hirudo medicinalis to human leukocyte elastase (EC 3.4.21.37), bovine alpha-chymotrypsin (EC 3.4.21.1) and subtilisin Carlsberg (EC 3.4.21.14) has been investigated. On lowering the pH from 9.5 to 4.5, values of Ka for eglin c binding to the serine proteinases considered decrease thus reflecting the acid-pK shift of the invariant histidyl catalytic residue (His57 in human leukocyte elastase and bovine alpha-chymotrypsin, and His64 in subtilisin Carlsberg) from congruent to 6.9, in the free enzymes, to congruent to 5.1, in the enzyme:inhibitor adducts. At pH 8.0, values of the apparent thermodynamic parameters for eglin c binding are: human leukocyte elastase - Ka = 1.0 x 10(10) M-1, delta G phi = -13.4 kcal/mol, delta H phi = +1.8 kcal/mol, and delta S phi = +52 entropy units; bovine alpha-chymotrypsin -Ka = 5.0 x 10(9) M-1, delta G phi = -13.0 kcal/mol, delta H phi = +2.0 kcal/mol, and delta S phi = +51 entropy units; and subtilisin Carlsberg - Ka = 6.6 x 10(9) M-1, delta G phi = -13.1 kcal/mol, delta H phi = +2.0 kcal/mol, and delta S phi = +51 entropy units (values of Ka, delta G phi and delta S phi were obtained at 21 degrees C; values of delta H phi were temperature independent over the range explored, i.e. between 10 degrees C and 40 degrees C; 1 kcal = 4184J).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biochemical Sciences, University of Rome La Sapienza, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Ascenzi
authors.forename: G
authors.initials: G
authors.lastname: Amiconi
authors.forename: E
authors.initials: E
authors.lastname: Menegatti
authors.forename: M
authors.initials: M
authors.lastname: Guarneri
authors.forename: M
authors.initials: M
authors.lastname: Bolognesi
authors.forename: H P
authors.initials: HP
authors.lastname: Schnebli
mesh_terms: D000818:Animals; D002417:Cattle; D002918:Chymotrypsin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011480:Protease Inhibitors / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism* / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism* / Q000494:pharmacology; D015843:Serpins; D013381:Subtilisins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D011480:Protease Inhibitors; D011506:Proteins; D011994:Recombinant Proteins; D015843:Serpins; C028656:eglin proteinase inhibitors; D013381:Subtilisins; D002918:Chymotrypsin; D010196:Pancreatic Elastase