Calcium-activated factor

Factor XIII. Factor XIII circulates in the blood as a zymogen composed of two pairs of different polypeptide chains designated A and B. Inert Factor XIII has a molecular weight of 350,000 daltons and is converted to its active transglutaminase form in the presence of thrombin and calcium. Activated Factor XIII, Xllla, induces an irreversible amide exchange reaction between the y-glutamine and S-lysine side chains of adjacent fibrin... 

Selected entries from Methods in Enzymology [vol, page(s)] Sulfonylation reaction, 11, 706 reaction kinetics, 11, 707 second-order rate constants for inactivation of chymotrypsin, trypsin, and acetylcholine esterase by PMSE and related sulfonylat-ing agents, 11, 707 reactivation of PMS-chymotrypsin, 11, 710 as inhibitor [of calcium-activated factor, 80, 674 of cathepsin G, 80, 565 of crayfish trypsin, 80, 639 of elastase, 80, 587 of pro-lylcarboxypeptidase, 80, 465 of protease Re, 80, 691 of protease So, 80, 695 of protein C, 80, 329] proteolysis, 76, 7. 

Extrinsic Pathway. Coagulation is initiated when tissue extracts with Hpid—protein properties are released from the membranes of endothehal cells following injury or insult. These substances, collectively designated tissue thromboplastin, complex with circulating Factor VII and in the presence of calcium ions subsequentiy activate Factor X (Fig. 1). In vitro evidence suggests that Factor X can be activated less rapidly through the interaction of kaUikrein [9001-01-8] with Factor VII. 

During ischaemia, NOS is activated by calcium influx or by cytokines like tumour necrosis factor (TNF) or by lipopolysaccharide (LPS) and NO is produced in excess. It has been proposed that the excitotoxic effect of glutamate, which contributes to ischaemia-induced neuronal damage, is mediated by increased production of NO via a chain of events that includes increases in intracellular calcium (via glutamate activation of NMDA receptors), calcium activation of NOS, production of NO and peroxynitrite, and induction of lipid peroxidation. In fact, N-nitro-L-atginine, a selective inhibitor of NOS, has been shown to prevent glutamate-induced neurotoxicity in cortical cell cultures (Dawson rf /., 1991). 

Mazer, B., Domenico, J., Sawami, H. and Gelfand, E.W. (1991) Platelet-activating factor induces an increase in intracellular calcium and expression of regulatory genes in human B lymphoblastoid cells. Journal of Immunology 146, 1914-1920. 

Gardner, C.R., Laskin, J.D., and Laskin, D.L., Platelet-activating factor-induced calcium mobilization and oxidative metabolism in hepatic macrophages and endothelial cells, J. Leukoc. Biol., 53, 190, 1993. 

Striibing C, Krapininsky G, Krapivinsky L, Clapham DE 2001 TRPC1 and TRPC5 form a novel cation channel in mammalian brain. Neuron 29 645-655 Trepakova ES, Csutora P, Hunton DL, Marchase RB, Cohen RA, Bolotina VM 2000 Calcium influx factor directly activates store-operated cation channels in vascular smooth muscle cells. J Biol Chem 275 26158-26163... 

Siegel RK. (1979). Ginseng abuse syndrome. Problems with the panacea. JAMA. 241(15) 1614-15. Simon MF, Chap H, Braquet P, Douste-Blazy L. (1987). Effect of BN 52021, a specific antagonist of platelet activating factor (PAF-acether), on calcium movements and phosphatidic acid production induced by PAF-acether in human platelets. Thromb Res. 45(4) 299-309. 

This calcium-activated enzyme [EC 3.4.21.75] catalyzes the hydrolysis of peptide bonds in protein precursors that results in the release of mature proteins from their proproteins by hydrolysis of ArgXaaYaaArg—Zaa bonds, where Xaa can be any amino acid and Yaa is an arginyl or a lysyl residue. Albumin, complement component C3, and von Willebrand factor are thus released from their respective precursors. Furin is a member of the peptidase family S8. 

Platelet membrane phosphatidylserine is critical to the formation of the tenase complex since on its surface activated factor VIII (Villa) generates a high-afflnity binding site for activated factor IX (IXa) in the presence of calcium. Subsequently, this complex activates factor X (2, 13). Platelet membrane phosphatidylserine similarly anchors activated factor V (Va), favoring the calcium-dependent binding of activated factor X (Xa). The prothrombinase complex is generated on the surface of the anionic platelet membrane phosphatidylserine when factor Va binds prothrombin. The prothrombinase complex cleaves prothrombin to produce thrombin, which has a multifunctional role (14). 

Purification entails use of an immunoaffinity column containing immobilized murine antifactor VII antibody. It is initially produced as an unactivated, single chain 406 amino acid polypeptide, which is subsequently proteolytically converted into the two-chain active factor Vila complex. After sterilization by filtration, the final product is aseptically filled into its final product containers and freeze-dried. The excipients present in the product include sodium chloride, calcium chloride, polysorbate 80, mannitol and glycylglycine. When freeze-dried in the presence of these stabilizing substances and stored under refrigerated conditions, the product displays a shelf-life of at least 2 years. It has proved effective in the treatment of serious bleeding events in patients displaying anti-factor VIII or IX antibodies. 

Hemostasis begins with the formation of the platelet plug, followed by activation of the clotting cascade, and propagation of the clot. One of the major multicomponent complexes in the coagulation cascade consists of activated factor IX (factor IXa) as the protease, activated factor VIII (factor Villa), calcium, and phospholipids as the cofactors, and factor X as the substrate. Factor IXa can be generated by either factor Xa activation of the intrinsic pathway or by the tissue factor/factor Vila complex. 

Boettger, M. K., Till, S., Chen, M. X., Anand, U., Otto, W. R., Plumpton, C., Trezise, D. J., Tate, S. N., Bountra, C., Coward, K., Birch, R., Anand, P. Calcium-activated potassium channel SK1-and IK1-like immunoreactivity in injured human sensory neurones and its regulation by neurotrophic factors, Brain 2002, 125, 252-260. 

PTH is a polypeptide hormone that is synthesized within the cells of the parathyroid glands. The primary factor controlling the release of PTH is the amount of calcium in the bloodstream.36 A calciumsensing receptor is located on the outer surface of the parathyroid cell membrane, and this receptor monitors plasma calcium levels.11,88 A decrease in plasma calcium activates this receptor and causes increased release of PTH. As blood calcium levels increase, the receptor is inhibited, and PTH release is reduced. 

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