title: Effect of single amino acid replacements on the thermodynamics of the reactive site peptide bond hydrolysis in ovomucoid third domain.
abstract: We have measured equilibrium constants, Khyd, at pN 6 for the hydrolysis of the reactive site peptide bond (bond between residues 18 and 19) in 42 sequenced variants (39 natural, 3 semisynthetic) of avian ovomucoid third domains. The values range from 0.4 to approximately 35. In 35 cases the effect of a single amino acid replacement on Khyd could be calculated, 13 are without effect and 22 range from a factor of 1.25 to 5.5. Several, but not all, of the effects can be rationalized in terms of residue-residue interactions that are affected by the reactive site hydrolysis. As the measurements are very precise it appears that additional measurements on designed rather than natural variants should allow for the precise measurement of side-chain--side-chain interaction energies.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN 47907.
authors.forename: W
authors.initials: W
authors.lastname: Ardelt
authors.forename: M
authors.initials: M
authors.lastname: Laskowski
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001717:Birds; D006031:Glycosylation; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D008969:Molecular Sequence Data; D010059:Ovomucin / Q000737:chemistry* / Q000648:ultrastructure; D012697:Serine Endopeptidases / Q000378:metabolism; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D010059:Ovomucin; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase