title: Structure of plasma and tissue kallikreins.
abstract: The kallikrein kinin system (KKS) consists of serine proteases involved in the production of peptides called kinins, principally bradykinin and Lys-bradykinin (kallidin). The KKS contributes to a variety of physiological processes including inflammation, blood pressure control and coagulation. Here we review the protein structural data available for these serine proteases and examine the molecular mechanisms of zymogen activation and substrate recognition focusing on plasma kallikrein (PK) and tissue kallikrein (KLK1) cleavage of kininogens. PK circulates as a zymogen bound to high-molecular-weight kininogen (HK). PK is activated by coagulation factor XIIa and then cleaves HK to generate bradykinin and factor XII to generate further XIIa.A structure has been described for the activated PK protease domain in complex with the inhibitor benzamidine. Kallikrein-related peptidases (KLKs) have a distinct domain structure and exist as a family of 15 genes which are differentially expressed in many tissues and the central nervous system.They cleave a wide variety of substrates including low-molecular-weight kininogen (LK) and matrix proteins. Crystal structures are available for KLK1, 3, 4, 5, 6 and 7 activated protease domains typically in complex with S1 pocket inhibitors. A substrate mimetic complex is described for KLK3 which provides insight into substrate recognition. A zymogen crystal structure determined for KLK6 reveals a closed S1 pocket and a novel mechanism of zymogen activation. Overall these structures have proved highly informative in understanding the molecular mechanisms of the KKS and provide templates to design inhibitors for treatment of a variety of diseases.
authors.affiliation: Dr. Jonas Emsley, Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, University Park, Nottingham, NG72RD, UK, Tel.: +44 1158467092, Fax: +44 1158468002, E-mail: jonas.emsley@nottingham.ac.uk.
authors.forename: M
authors.initials: M
authors.lastname: Pathak
authors.forename: S S
authors.initials: SS
authors.lastname: Wong
authors.forename: I
authors.initials: I
authors.lastname: Dreveny
authors.forename: J
authors.initials: J
authors.lastname: Emsley
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001794:Blood Pressure; D002384:Catalysis; D020134:Catalytic Domain; D004792:Enzyme Precursors / Q000737:chemistry; D015956:Factor XIIa / Q000737:chemistry; D006801:Humans; D007249:Inflammation; D016234:Kallikrein-Kinin System; D007704:Kininogens / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry; D020842:Plasma Kallikrein / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D057057:Serine Proteases / Q000737:chemistry; D013379:Substrate Specificity; D020840:Tissue Kallikreins / Q000737:chemistry*
chemical_list: D004792:Enzyme Precursors; D007704:Kininogens; D010447:Peptide Hydrolases; D057057:Serine Proteases; D020842:Plasma Kallikrein; D020840:Tissue Kallikreins; D015956:Factor XIIa