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PubMed · 77809

[Factor XII (HAGEMAN FACTOR)].

F Kase·P Klír·J Pospísil·P Poucková
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Abstract

The discovery of factor XII (Hageman factor), the attempts of characterizing it, the knowledge of its presence of absence in the various vertebrate classes are represented in a survey and recent opinions of molecular biology about its structure and composition are discussed. The effect of the activating substances for transferring the Hageman factor into its active form are represented with the role of the pre-kallikrein (Fletcher factor) and of the highly molecular kininogen (Fitzgerald factor) being referred to. Furthermore, the following systems influenced by factor XII are dealt with: 1. The endogenous and exogenous activating system of blood clotting and possible reasons for lower bleedings with factor XII deficiency. 2. Role of the Hageman factor in activating fibrinolysis. 3. Influence on the liberation of kinin. 4. Correlations towards the complement system. 5. Possible inhibitory effect of platelet aggregation. Finally the close connection of all these systems is referred to and the necessity of considering these complicated events in a complex way is stressed.

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Blood CoagulationComplement System ProteinsEnzyme ActivationFactor XIIFactor XII DeficiencyFibrinolysisHumansKallikreinsKininsMolecular ConformationPlatelet AggregationEnglish AbstractJournal ArticleReview

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F Kase, P Klír, J Pospísil, P Poucková. 1978. [Factor XII (HAGEMAN FACTOR)].. https://pubmed.ncbi.nlm.nih.gov/77809/

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Diffusion control in blood coagulation. Activation of factor X by factors IXa/VIIIa assembled on human monocyte membranes.

This study examines mechanisms that regulate the activation of blood coagulation proteases on intact cell membranes. The activation of factor X by factors IXa and VIIIa assembled on viable monocytes is presented as a biologically relevant model for membrane-dependent proteolysis of coagulation zymogens. The hypothesis that this reaction is limited by diffusion was tested by comparing predicted with observed concentration dependence, temperature dependence, and effective rate coefficient. Rates of factor X catalysis were measured using a chromogenic substrate specific for the product, factor Xa. The value of KR and of K1/2, i.e. concentrations giving half-maximal rates in reciprocal functional titrations with substrate and enzyme, respectively, were directly correlated with the concentration of the titrated component. Arrhenius plots constructed over temperatures encompassing 10-35 degrees C were biphasic with downward concavity. Apparent activation energies were 6.01 +/- 0.93 and 35.84 +/- 8.9 kcal/mol for the interval above and below the inflection point, respectively. The effective rate coefficient calculated from apparent kinetic parameters was 3.58 +/- 0.1 x 10(12) M-1 s-1. This rate is similar to the maximal rate of collision between factor X molecules and the monocyte, i.e. 2.9 x 10(12) M-1 s-1 estimated from the steady-state von Smoluchowski equation for uniformly reacting spherical particles. The observed agreement between predicted and experimental results indicates that under biologically relevant conditions, the rate of factor X activation by the intrinsic protease is controlled by diffusion of factor X toward the catalytic site.

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