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Biomedical subjects

J Jesty

Publications and source records attributed to J Jesty.

45 records · Page 3Linked to original sources
PubMed1975

The activation of coagulation factor X. Identity of cleavage sites in the alternative activation pathways and characterization of the COOH-terminal peptide.

Bovine Factor X can be activated by two alternative pathways. The first, favored at high concentrations of the complex of tissue factor and Factor VII, is initiated by the action of Factor VII on Factor X to cleave an activation peptide from the NH2 terminus of the heavy chain, to produce alpha-Xa. This is then converted autocatalytically to another form of Factor Xa, beta-Xa, by the loss of a 17-residue glycopeptide from the COOH terminus of the heavy chain, in a lipid-dependent reaction. The alternative pathway, favored at lower activator concentrations, is initiated by the action of Factor Xa on Factor X, in the presence of lipid, to release the same COOH-terminal peptide as is produced in the conversion of alpha-Xa to beta-Xa. The intermediate produced by the loss of this peptide from Factor X,I1, can be activated directly to beta-Xa by the tissue factor-Factor VII complex, with the loss of the same NH2-terminal peptide as is produced in the conversion of Factor X to alpha-Xa. The autocatalytic activation of Factor X by Factor Xa described previously occurs to a marked extent only at very low activator concentrations, and has been shown to proceed largely by the loss of the normal NH2-terminal peptide from the heavy chain of I1-Initial experiments show that neither peptide affects the rate of coagulation by either the extrinsic or intrinsic pathways. The amino acid sequences have been determined on both sides of the peptide cleavages, and it has been shown that the cleavage sites are the same, regardless of the pathway of activation. The amino acid sequence and carbohydrate composition of the COOH-terminal peptide have been determined. The carbohydrate moiety is attached via an O-glycosidic linkage at a threonine residue, and contains galactosamine but no glucosamine.

Amino Acid Sequence↗
PubMed1974

Self-damping mechanism in blood coagulation.

Two reactions of the extrinsic pathway of coagulation, the activations of Factor X and prothrombin, have been studied in purified systems and shown to be self-damping. Factor X was activated by the tissue factor-Factor VII complex, and prothrombin by two systems: the coagulant protein of Taipan venom, and the physiological complex of activated Factor X, Factor V, lipid, and calcium ions. In each case the yield of enzyme, activated Factor X or thrombin, is a function of the concentration of activator. These and other observations are considered as a basis for a control mechanism in coagulation.

Blood Coagulation↗
PubMed1973

A method for the simultaneous isolation of factor X and prothrombin from bovine plasma.

1. A method is described for the simultaneous isolation of both Factor X and prothrombin from bovine plasma. The proteins are adsorbed on and eluted from barium sulphate and chromatographed on DEAE-Sephadex and are finally purified by rechromatography on DEAE-Sephadex. 2. The proteins can be purified in 48h from the collection of the blood and the method can be used to process large volumes of plasma. 3. The prothrombin has a molecular weight of 70300; the Factor X, on the other hand, is polydisperse, with most of the protein (86%) having a molecular weight of 56000.

Animals↗
PubMed1973

The preparation of activated factor X and its action on prothrombin.

The preparation of activated Factor X from reaction mixtures of bovine Factor X and Russell's-viper venom is described. The molecular weight of purified protein varies about a mean value of 40000; this variation is the result of at least two forms of Factor Xa. The action of activated Factor X, together with purified Factor V, was studied on purified prothrombin and the reaction products were isolated. In addition to thrombin, two other polypeptides with molecular weights of 16000 and 19500 were recovered.

Animals↗
PubMedDate not supplied

Deficiency of plasma protein S, protein C, or antithrombin III and arterial thrombosis.

Protein C and protein S are vitamin K-dependent coagulation factors that together act as an anticoagulant, and antithrombin III is a plasma protein that inhibits several activated factors in the coagulation cascade. Although deficiencies of any of these three proteins have been associated with deficiencies of these factors. We report one patient with a protein S deficiency, another with a protein C deficiency, and a third with an antithrombin III deficiency, each of whom who had extensive arterial thrombosis. We suggest that deficiencies of these proteins may constitute risk factors for arterial thrombosis.

Adult↗