1. The kallikrein-like activity of Heloderma venom is inhibited by carbon monoxide
Vance G Nielsen,Nathaniel Frank J Thromb Thrombolysis . 2019 May;47(4):533-539. doi: 10.1007/s11239-019-01853-6.
Lizards in the genus Heloderma are the most ancient venomous reptiles, with a traceable lineage nearly 100 million years old. The proteome of the venom of three of the remaining species (Heloderma suspectum, H. exasperatum, H. horridum) are very conserved, with kallikrein-like activity present to cause critical hypotension to immobilize and outright kill prey. Kallikrein-like activity would be expected to activate the contact protein pathway of coagulation, which would be detectable with thrombelastography in human plasma. Thus, it was proposed to determine if kallikrein-like activity could be detected with thrombelastography, and if this activity could be inhibited by carbon monoxide (CO) via a putative heme-based mechanism. Procoagulant activity of each venom was assessed via thrombelastography with normal plasma, and kallikrein-like activity confirmed with FX-depleted plasma. Venom was then exposed to carbon monoxide releasing molecule-2 (CORM-2) or its inactive releasing molecule to assess CO inhibition. All three venoms demonstrated kallikrein-like activity with the same potency and inhibition of activity by CO. In conclusion, the present work documented that procoagulant, kallikrein-like activity containing venoms of the oldest species of venomous reptiles was inhibited by CO, potentially via heme modulation. This is also the first identification and characterization of a kallikrein-like enzyme utilizing coagulation factor-depleted plasma to assess venom that inflicts hypotension. Future investigations will continue to define the vulnerability of venom enzymatic activities to CO.
2. Kallikrein inhibition and C1-esterase inhibitor levels in patients with the lupus inhibitor
K C Meyer,A A Killeen,J R Edson,J M Vogt Am J Clin Pathol . 1987 Aug;88(2):223-8. doi: 10.1093/ajcp/88.2.223.
It has been suggested that kallikrein inhibition may predispose patients with the lupus inhibitor to thrombosis by interfering with the Factor XII-mediated activation of plasminogen. To further investigate this suggestion, the authors measured kallikrein inhibition in 19 patients with the lupus inhibitor. They found that kallikrein inhibition was greater than 100% of that of a normal plasma pool in all patients and greater than 125% in 11 of 19. Kallikrein inhibition was significantly correlated with C1-esterase inhibitor (C1S-INH) concentration, which they measured by rocket immunoelectrophoresis (r = +0.55, P less than 0.05). In three patients the C1S-INH was more than 30% greater than the kallikrein inhibition. Crossed immunoelectrophoresis for C1S-INH in these patients' plasma revealed an electrophoretic mobility identical with that of the normal plasma pool. The authors suggest that C1S-INH-mediated kallikrein inhibition, in conjunction with other coagulation abnormalities, predisposes patients with the lupus inhibitor to thrombosis.
3. Tissue kallikrein inhibitors in mammals
K X Chai,L Chao,J Chao Immunopharmacology . 1996 May;32(1-3):67-72. doi: 10.1016/0162-3109(96)00010-0.
We have discovered, purified and cloned a new kallikrein-binding protein (KBP or kallistatin) from humans and rodents. Kallistatins are members of the serine proteinase inhibitor (serpin) superfamily. They are acidic glycoproteins with molecular masses of 58-62 kDa and pI values of 4.6-5.2. Kallistatin forms a SDS-stable complex with tissue kallikrein and inhibits kallikrein's activities. Human kallistatin has a unique cleavage site with Phe-Phe-Ser at the P2-P1-P1' positions. The protein sequence of mature human kallistatin shares 44-46% identity with other serpins such as human alpha 1-antitrypsin, protein C inhibitor and rat kallikrein-binding protein. The kallistatin genes display the typical five exon-four intron serpin gene structure. The human kallistatin gene is localized on chromosome 14q31-32.1 and the RKBP gene is on chromosome 6. Kallistatin is evolutionarily diverse but functionally conserved in mammalian species. This overview summarizes the biochemistry, molecular biology and potential physiology and/or pathophysiology of this new tissue kallikrein inhibitor.
4. Kallikrein inhibitors
E Truscheit,H Fritz,E Fink Fed Proc . 1979 Dec;38(13):2753-9.
So far the Cl inactivator, alpha 2-macroglobulin, antithrombin III (in the presence of heparin), and alpha 1-antitrypsin have been identified as inhibitors of plasma kallikrein; alpha 1-antitrypsin reacts slowly also with tissue kallikreins. Of the various naturally occurring kallikrein inhibitors the basic trypsin-kallikrein inhibitor of bovine organs, aprotinin (the active substance of Trasylol), has attained by far the most interest. This inhibitor, which is produced by mast cells, has unusual properties due to its compact tertiary structure. Additional topics of aprotinin and structurally related inhibitors discussed are the mechanism of enzyme-inhibitor complex formation, the production of chemical mutants of aprotinin, the structural basis of kallikrein inhibition, and selected aspects regarding aprotinin medication.
