title: Protein engineering thrombin for optimal specificity and potency of anticoagulant activity in vivo.
abstract: Previous alanine scanning mutagenesis of thrombin revealed that substitution of residues W50, K52, E229, and R233 (W60d, K60f, E217, and R221 in chymotrypsinogen numbering) with alanine altered the substrate specificity of thrombin to favor the anticoagulant substrate protein C. Saturation mutagenesis, in which residues W50, K52, E229, and R233 were each substituted with all 19 naturally occurring amino acids, resulted in the identification of a single mutation, E229K, that shifted the substrate specificity of thrombin by 130-fold to favor the activation of the anticoagulant substrate protein C over the procoagulant substrate fibrinogen. E229K thrombin was also less effective in activating platelets (18-fold), was resistant to inhibition by antithrombin III (33-fold and 22-fold in the presence and absence of heparin), and displayed a prolonged half-life in plasma in vitro (26-fold). Thus E229K thrombin displayed an optimal phenotype to function as a potent and specific activator of endogenous protein C and as an anticoagulant in vivo. Upon infusion in Cynomolgus monkeys E229K thrombin caused an anticoagulant effect through the activation of endogenous protein C without coincidentally stimulating fibrinogen clotting and platelet activation as observed with wild-type thrombin. In addition, E229K thrombin displayed enhanced potency in vivo relative to the prototype protein C activator E229A thrombin. This enhanced potency may be attributable to decreased clearance by antithrombin III, the principal physiological inhibitor of thrombin.
authors.affiliation: Gilead Sciences Inc., Foster City, California 94404, USA.
authors.forename: M
authors.initials: M
authors.lastname: Tsiang
authors.forename: L R
authors.initials: LR
authors.lastname: Paborsky
authors.forename: W X
authors.initials: WX
authors.lastname: Li
authors.forename: A K
authors.initials: AK
authors.lastname: Jain
authors.forename: C T
authors.initials: CT
authors.lastname: Mao
authors.forename: K E
authors.initials: KE
authors.lastname: Dunn
authors.forename: D W
authors.initials: DW
authors.lastname: Lee
authors.forename: S Y
authors.initials: SY
authors.lastname: Matsumura
authors.forename: M D
authors.initials: MD
authors.lastname: Matteucci
authors.forename: S E
authors.initials: SE
authors.lastname: Coutré
authors.forename: L L
authors.initials: LL
authors.lastname: Leung
authors.forename: C S
authors.initials: CS
authors.lastname: Gibbs
mesh_terms: D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology*; D001777:Blood Coagulation / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D005340:Fibrinogen / Q000378:metabolism; D006207:Half-Life; D006801:Humans; D007700:Kinetics; D008252:Macaca fascicularis; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D015539:Platelet Activation / Q000187:drug effects; D011486:Protein C / Q000378:metabolism; D011487:Protein Conformation; D015202:Protein Engineering; D013379:Substrate Specificity; D013917:Thrombin / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000925:Anticoagulants; D011486:Protein C; D005340:Fibrinogen; D013917:Thrombin