Kallikrein-kinin cascadeBiological Processkallikrein_kinin_cascade
Connections
Surface-bound factor XIIa is the protease that cleaves prekallikrein to kallikrein.
Reciprocal feedback: formed kallikrein activates further factor XII far faster than the surface alone, amplifying the contact phase (PMID:273926, PMID:386794).
Active plasma kallikrein is the enzyme of the plasma route of kinin release. The tissue route does not depend on this step.
Released bradykinin and kallidin are the agonists of the B2 receptor.
The intact kinins are the substrates of carboxypeptidases N and M.
The des-Arg kinins are the agonists of the inducible B1 receptor, so this step switches the signal from B2 to B1 rather than only terminating it.
ACE, neprilysin and aminopeptidase P destroy kinin activity; ACE sits in a complex with the B2 receptor itself (PMID:17077303).
C1 inhibitor and alpha-2-macroglobulin inactivate kallikrein and factor XIIa, shutting down the plasma route.
Kallistatin blocks tissue kallikrein's action on kininogen, and C1 inhibitor and A2M block plasma kallikrein's.
Part 1: contact activation of factor XII
Part 2: prekallikrein activation
Activation of plasma prekallikrein to kallikreinReactionkks_prekallikrein_activation
Prekallikrein circulates bound to high-molecular-weight kininogen, which assembles it next to surface-bound factor XII. F12a cleaves it to kallikrein; on endothelial cells, membrane-expressed prolylcarboxypeptidase does the same independently of factor XII.
Annotons
Factor XIIa activation of prekallikrein
f12a_pk_activation
Participant: Gene Product: F12
Function
Processes
Locations
First committed step of the plasma route. The surface-bound alpha form of F12a activates prekallikrein and factor XI; the soluble beta form activates prekallikrein only, which disseminates kinin formation while keeping intrinsic clotting local.
PMID:386794High-molecular-weight kininogen assembles prekallikrein next to surface-bound factor XII, and the two F12a forms differ in which substrates they reach.
High MW kininogen serves as a surface cofactor to assemble prekallikrein or factor XI in proximity to surface-bound Hageman factor.
PMID:386794Soluble beta-F12a leaves the surface and activates further prekallikrein but not factor XI, separating the kinin output from intrinsic clotting.
The other form of activated Hageman factor, beta HFa, leaves the surface, going into solution where it readily activates additional prekallikrein but not factor XI.
PMID:18725990In patients with systemic amyloidosis, factor XII but not factor XI is activated and kallikrein is formed, showing the two outputs can be uncoupled in vivo.
we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis
Prolylcarboxypeptidase activation of prekallikrein on endothelium
prcp_pk_activation
Participant: Gene Product: PRCP
Function
Processes
Locations
Factor XII-independent entry to the cascade: membrane-expressed PRCP activates prekallikrein that has assembled on high-molecular-weight kininogen at the endothelial surface, with a Km in the nanomolar range.
PMID:11830581PRCP was purified from endothelial cells as the prekallikrein activator acting on kininogen-bound prekallikrein.
When prekallikrein (PK) assembles on high molecular weight kininogen on HUVEC, PK is activated to kallikrein.
PMID:11830581The activity is not factor XII: it does not correct factor XII-deficient plasma, is not recognised by anti-factor XII and does not activate factor XI.
PKA did not correct the coagulant defect in factor XII deficient plasma, was purified from HUVEC cultured in factor XII-deficient serum, was not detected by antibody to factor XII, did not activate FXI, and was not inhibited by a neutralizing antibody to FXII.
PMID:11830581PRCP activates prekallikrein with nanomolar affinity.
The K(m) of PK activation by PRCP is 6.7 nm.
Part 3: kinin release from kininogen
Release of kinins from kininogen by a kallikreinReactionkks_kinin_release
Both active kinins come from kininogen (KNG1), whose alternative transcripts give the high- and low-molecular-weight forms. Which kinin is produced depends on which kallikrein does the cleaving, so the two routes are modeled as alternatives along the enzyme axis. Both can operate in the same organism, in different compartments.
Variant set: Plasma versus tissue kallikrein route by enzyme and substrate route (One Or More)
ONE_OR_MORE rather than EXACTLY_ONE: the plasma route operates in the intravascular compartment on high-molecular-weight kininogen and the tissue route in glandular tissue and their fluids on the low-molecular-weight form, and tissue kallikrein can also cleave the high form. A concrete realization may therefore have one or both.
Plasma kallikrein releasing bradykinin from high-molecular-weight kininogenReactionplasma_kallikrein_route
Active plasma kallikrein cleaves high-molecular-weight kininogen in the intravascular compartment, liberating the nonapeptide bradykinin and leaving the disulfide-linked kinin-free heavy and light chains.
Annotons
Plasma kallikrein cleavage of high-molecular-weight kininogen
klkb1_hk_cleavage
Participant: Gene Product: KLKB1
Function
Processes
Locations
Product-forming step of the plasma route; the enzyme performs the cleavage, kininogen is its substrate.
PMID:104988Human plasma kallikrein liberates kinin from human high-molecular-weight kininogen.
We investigated whether the liberation of kinin from human HMW-kininogen by human plasma kallikrein was accompanied by liberation of histidine-rich fragments
PMID:104988Bradykinin is isolated from the digest, with the histidine-rich sequence staying on the light chain of the kinin-free protein.
Most of the histidine in human HMW-kininogen was recovered in the kinin-free protein, and the light chain of kinin-free protein was found to be rich in histidine compared with the heavy chain.
Tissue kallikrein releasing kallidin from low-molecular-weight kininogenReactiontissue_kallikrein_route
Tissue kallikrein, secreted by kidney, pancreas and salivary gland, cleaves low-molecular-weight kininogen at two sites, one of them the unusual Met-Lys bond, releasing the decapeptide kallidin (Lys-bradykinin).
Annotons
Tissue kallikrein cleavage of low-molecular-weight kininogen
klk1_lk_cleavage
Participant: Gene Product: KLK1
Function
Processes
Locations
Product-forming step of the tissue route. Cleavage at site II (Met-Lys) is unique to tissue kallikrein and is what makes the product a decapeptide with an N-terminal lysine.
PMID:7749384Tissue kallikrein cleaves low-molecular-weight kininogen at two sites to release kallidin, one of them the TK-specific Met-Lys bond.
Tissue kallikrein (TK) cleaves low molecular weight kininogen (LK) at two sites to release kallidin
PMID:7749384Site I is a trypsin-like Arg-Ser bond and site II the unusual Met-Lys bond unique to tissue kallikrein.
site I (between Arg389 and Ser390) is a typical cleavage point for a trypsin-like enzyme whereas site II (between Met379 and Lys380) is unusual and unique to TK
PMID:2686621The salivary, pancreatic and renal tissue kallikreins are one protein, cloned and shown to be proteolytically active.
The protein was identified by Western-blot analysis and by demonstration of its specific proteolytic activity.
Part 4: kinin receptor signaling
Kinin signaling through the B2 and B1 bradykinin receptorsSignaling Pathwaykks_kinin_signaling
The released kinins act as short-lived local hormones. Bradykinin and kallidin are agonists of the constitutively expressed B2 receptor; the des-Arg metabolites made in part 5 are the agonists of the inducible B1 receptor. Both are G protein-coupled receptors that raise intracellular calcium and drive vasodilation and inflammatory mediator release.
Annotons
Kinin released from kininogen acting as a local hormone
kng1_kinin_hormone
Participant: Gene Product: KNG1
Function
Processes
Locations
The one step kininogen itself performs: its bradykinin moiety, once released, is the receptor agonist. Kininogen is the substrate of the kallikreins, not a participant in their proteolysis, so it carries no processing term here.
PMID:1314587Bradykinin binds the cloned human B2 receptor with sub-nanomolar affinity, the agonist activity annotated to KNG1 by IDA.
Saturation binding analysis indicates that the human BK-2 receptor expressed in COS-7 cells binds BK with a KD of 0.13 nM.
B2 bradykinin receptor signaling
bdkrb2_signaling
Participant: Gene Product: BDKRB2
Function
Processes
Locations
Constitutively expressed receptor for the intact kinins bradykinin and kallidin; couples to the calcium-phosphatidylinositol cascade.
PMID:1329734The cloned human B2 receptor is a high-affinity bradykinin receptor coupling to calcium and inositol phosphate signaling.
Functional coupling to the Ca(2+)-phosphatidylinositol cascade was demonstrated in transfected CHO cells where inositol phosphates accumulation and intracellular calcium concentration were elevated in response to BK stimulation.
PMID:1314587The receptor is a seven-transmembrane G protein-coupled receptor of the B2 subtype.
The cDNA clone encodes a 364 amino acid protein that has the characteristics of a seven transmembrane domain G-protein coupled receptor.
PMID:17077303ACE and the B2 receptor form a complex at the plasma membrane, placing the receptor and its kininase side by side at the cell surface.
Human ACE and bradykinin B2 receptors form a complex at the plasma membrane.
B1 bradykinin receptor signaling
bdkrb1_signaling
Participant: Gene Product: BDKRB1
Function
Processes
G protein-coupled receptor signaling pathwayGO:0007186 Locations
Inducible receptor whose agonists are the des-Arg kinins produced in part 5; in human the dominant ligand is des-Arg10-kallidin.
PMID:10422787The cloned human B1 receptor is characterised with the des-Arg kinin ligand des-Arg10-kallidin.
A ligand binding assay with [3H]des-Arg10-kallidin was used to compare their pharmacology with respect to known bradykinin B1 and B2 receptor ligands.
PMID:10422787Kallidin and its des-Arg derivatives are the major physiological B1 ligands in human, bradykinin-derived ones in rat.
the presence of T-kinin, bradykinin and their des-Arg derivatives as the major physiological peptides in rat and the predominance of kallidin and its derivatives in human
Part 5: carboxy-terminal processing to des-Arg kinins
Carboxypeptidase removal of the C-terminal arginine from kininsReactionkks_des_arg_generation
Two basic-residue carboxypeptidases remove the C-terminal arginine of bradykinin and kallidin: plasma carboxypeptidase N (kininase I) and the GPI-anchored carboxypeptidase M at cell surfaces. The products lose B2 agonism but are the agonists of the B1 receptor, so this step converts rather than only destroys the signal.
Annotons
Carboxypeptidase N (kininase I) removal of C-terminal Arg
cpn1_des_arg
Participant: Gene Product: CPN1
Function
Processes
Locations
The plasma kininase I activity; the catalytic small subunit is held in a 280 kDa complex with large subunits that stabilise it in plasma.
PMID:2912725Carboxypeptidase N, the plasma kininase 1, is a metalloprotease whose catalytic small subunits sit in a large plasma complex.
The human plasma metallo-protease carboxypeptidase N of Mr 280,000 consists of two small, enzymatically active subunits of Mr 50,000 and two large subunits.
Carboxypeptidase M removal of C-terminal Arg at the cell surface
cpm_des_arg
Participant: Gene Product: CPM
Function
Processes
Locations
Membrane-anchored kininase I-type enzyme; being on the plasma membrane at neutral pH, it can convert kinins immediately next to their receptors.
PMID:2914904Purified human carboxypeptidase M is a membrane-bound metallopeptidase that cleaves the C-terminal Arg or Lys of peptides including bradykinin.
bradykinin (Km = 16 microM, kcat = 147 min-1)
PMID:2914904Its membrane localization and neutral pH optimum let it modulate peptide hormones at the receptor.
Because of its localization on the plasma membrane and optimal activity at neutral pH, carboxypeptidase M could inactivate or modulate the activity of peptide hormones either before or after their interaction with plasma membrane receptors.
PMID:2394713The kininase I-type activity that inactivates bradykinin by releasing Arg9 in kidney cells is carboxypeptidase M.
Cultured Madin-Darby canine kidney (MDCK) distal tubular cells contain a kininase I-type enzyme that inactivates bradykinin by releasing Arg9. We found the properties of this kininase to be identical with carboxypeptidase M.
Part 6: kinin inactivation by kininases
Destruction of kinin activity by kininasesReactionkks_kinin_inactivation
Cleavage of any peptide bond of bradykinin abolishes its B2 agonism, so several unrelated peptidases act in parallel as kininases: ACE (kininase II) removes C-terminal dipeptides, neprilysin cleaves internally, and membrane-bound aminopeptidase P (XPNPEP2) removes the N-terminal residue before the proline. Which one dominates depends on localization and access.
Annotons
ACE (kininase II) degradation of bradykinin
ace_kininase
Participant: Gene Product: ACE
Function
Processes
Locations
The classical kininase II. Both of its active sites hydrolyse bradykinin, and more efficiently than angiotensin I, which is why ACE inhibition raises kinin levels.
PMID:7683654Both ACE active sites convert bradykinin to BK1-7 and BK1-5, with higher efficiency than for angiotensin I.
Both active sites converted bradykinin (BK) to BK1-7 and BK1-5 with similar kinetics and with Kappm at least 30 times lower and kcat/kappm 10 times higher than for AI.
PMID:1282629Angiotensin I-converting enzyme is one of the peptidases that degrade bradykinin.
These include aminopeptidase P, meprin, endopeptidase 24.15, prolyl endopeptidase, neutral endopeptidase 24.11, angiotensin I-converting enzyme, carboxypeptidase N, carboxypeptidase M, and deamidase.
Neprilysin cleavage of kinins
mme_kininase
Participant: Gene Product: MME
Function
Processes
Locations
Neutral endopeptidase 24.11; an internal cut is enough to abolish kinin activity, and neprilysin is one of the kininases targeted together with ACE by vasopeptidase inhibitors.
PMID:1282629Neutral endopeptidase 24.11 is among the bradykinin-degrading peptidases, and any peptide-bond cleavage inactivates the kinin.
Because bradykinin is inactivated (for binding the B2 receptor) when any of its peptide bonds are cleaved, all of these enzymes qualify as potential "kininases" in vivo
Membrane-bound aminopeptidase P degradation of kinins
xpnpep2_kininase
Participant: Gene Product: XPNPEP2
Function
Processes
Locations
GPI-anchored vascular form of aminopeptidase P, whose natural substrates are the kinins; its activity is the clinical correlate of ACE-inhibitor-associated angioedema risk.
PMID:15361070Aminopeptidase P cleaves the N-terminal residue of peptides with proline at P1', and the kinins are its natural substrates.
APP (aminopeptidase P) has the unique ability to cleave the N-terminal amino acid residue from peptides exhibiting a proline at P(1)'.
PMID:15361070The engineered soluble form of the human membrane-bound enzyme is fully functional and its substrates are the kinins.
we synthesized three internally quenched fluorescent peptide substrates that exhibit a similar affinity for the enzyme than its natural substrates, the kinins
Part 7: inhibition of the cascade proteases
Serpin and alpha-2-macroglobulin control of the kallikreins and factor XIIaRegulatory Stepkks_protease_inhibition
The cascade is held off by inhibitors of its proteases rather than of its peptides. C1 inhibitor is the principal regulator of factor XIIa and plasma kallikrein, alpha-2-macroglobulin traps kallikrein by conformational capture, and kallistatin inhibits tissue kallikrein.
Annotons
C1 inhibitor inhibition of factor XIIa and plasma kallikrein
serping1_inhibition
Participant: Gene Product: SERPING1
Function
serine-type endopeptidase inhibitor activityGO:0004867 Processes
negative regulation of endopeptidase activityGO:0010951 Locations
The principal plasma regulator of contact activation; its deficiency causes hereditary angioedema, a bradykinin-mediated disease, which is the clinical demonstration that this is the module's main brake.
PMID:7692967C1 inhibitor and alpha-2-macroglobulin are kallikrein's primary plasma inhibitors, with second-order rate constants of 1.7e4 and 3.4e4 M-1 s-1.
nor did the protein enhance the rate constants of 1.7 x 10(4) and 3.4 x 10(4) M-1 s-1 for kallikrein reactions with its primary plasma inhibitors C1-inhibitor and alpha 2-macroglobulin, respectively
PMID:7692967In plasma, kallikrein is partitioned predominantly into C1-inhibitor and alpha-2-macroglobulin complexes.
significantly altered the partitioning of radiolabeled kallikrein from predominantly C1-inhibitor and alpha 2-macroglobulin complexes (86-92%) to mostly antithrombin complexes (50-53%)
Alpha-2-macroglobulin trapping of plasma kallikrein
a2m_inhibition
Participant: Gene Product: A2M
Function
Processes
negative regulation of endopeptidase activityGO:0010951 Locations
Broad-spectrum trap rather than a serpin: bait-region cleavage collapses the tetramer around the protease. Together with C1 inhibitor it accounts for most kallikrein inhibitory capacity of plasma. This matches the core function of its gene review (genes/human/A2M/).
PMID:7692967Alpha-2-macroglobulin is one of kallikrein's two primary plasma inhibitors.
its primary plasma inhibitors C1-inhibitor and alpha 2-macroglobulin
PMID:7692967In plasma most kallikrein ends up trapped in C1-inhibitor and alpha-2-macroglobulin complexes.
predominantly C1-inhibitor and alpha 2-macroglobulin complexes (86-92%)
Kallistatin inhibition of tissue kallikrein
serpina4_inhibition
Participant: Gene Product: SERPINA4
Function
serine-type endopeptidase inhibitor activityGO:0004867 Processes
negative regulation of endopeptidase activityGO:0010951 Locations
The serpin specific to the tissue route: it forms an equimolar complex with tissue kallikrein and blocks its action on kininogen; heparin abolishes the inhibition.
PMID:1334488Kallistatin inhibits human tissue kallikrein acting on kininogen, in an equimolar serpin complex.
Kallistatin inhibits human tissue kallikrein's activity toward kininogen and tripeptide substrates.
PMID:1334488Heparin blocks kallistatin's inhibition of tissue kallikrein.
Heparin blocks kallistatin's complex formation with tissue kallikrein and abolishes its inhibitory effect on tissue kallikrein's activity.