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Title: Multiple active forms of thrombin. IV. Relative activities of meizothrombins

Abstract

The prothrombin activation intermediates meizothrombin and meizothrombin(desF1) (meizothrombin that has been autoproteolyzed to remove fragment 1) have been obtained in a relatively pure, active form with minimal autolysis, making them suitable for enzymatic characterization. When compared at equimolar concentrations, alpha-thrombin, fragment 1.2+ alpha-thrombin, meizothrombin(desF1), and meizothrombin have approximately 100, 100, 10, and 1% activity, respectively, toward the macromolecular substrates factor V, fibrinogen, and platelets. The difference in activity of these four enzymes cannot be attributed to alterations in the catalytic triad, as all four enzymes have nearly identical catalytic efficiency toward the chromogenic substrate S2238. Further, the ability of meizothrombin and meizothrombin(desF1) to activate protein C was 75% of the activity exhibited by alpha-thrombin or fragment 1.2+ alpha-thrombin. All four enzymes bind to thrombomodulin, as judged by the enhanced rate of protein C activation upon preincubation of the enzymes with thrombomodulin. The extent of rate enhancement varied, with meizothrombin/thrombomodulin exhibiting only 50% of the alpha-thrombin/thrombomodulin rate. This difference in rate is not due to a decreased affinity of the meizothrombin for thrombomodulin since the apparent dissociation constants for the alpha-thrombin-thrombomodulin complex and the meizothrombin-thrombomodulin complex are virtually identical. The difference in the observed rate is due in part to themore » higher Km for protein C exhibited by the meizothrombin-thrombomodulin complex. Incubation of the thrombomodulin-enzyme complex with phospholipid vesicles caused an increase in the protein C activation rates. The kinetic constants for protein C activation in the presence of phospholipid are virtually identical for these enzyme-thrombomodulin complexes.« less

Authors:
;  [1]
  1. Univ. of Vermont College of Medicine, Burlington (USA)
Publication Date:
OSTI Identifier:
6718609
Resource Type:
Journal Article
Journal Name:
Journal of Biological Chemistry; (USA)
Additional Journal Information:
Journal Volume: 265:18; Journal ID: ISSN 0021-9258
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; PEPTIDE HYDROLASES; ENZYME ACTIVITY; PROTHROMBIN; THROMBIN; AUTORADIOGRAPHY; BIOCHEMICAL REACTION KINETICS; CATTLE; IODINE ISOTOPES; MOLECULAR WEIGHT; PHOSPHOLIPIDS; PRECURSOR; ANIMALS; BLOOD COAGULATION FACTORS; COAGULANTS; DOMESTIC ANIMALS; DRUGS; ENZYMES; ESTERS; HEMATOLOGIC AGENTS; HEMOSTATICS; HYDROLASES; ISOTOPES; KINETICS; LIPIDS; MAMMALS; ORGANIC COMPOUNDS; ORGANIC PHOSPHORUS COMPOUNDS; PROTEINS; REACTION KINETICS; RUMINANTS; SERINE PROTEINASES; VERTEBRATES; 550201* - Biochemistry- Tracer Techniques

Citation Formats

Doyle, M F, and Mann, K G. Multiple active forms of thrombin. IV. Relative activities of meizothrombins. United States: N. p., 1990. Web.
Doyle, M F, & Mann, K G. Multiple active forms of thrombin. IV. Relative activities of meizothrombins. United States.
Doyle, M F, and Mann, K G. Mon . "Multiple active forms of thrombin. IV. Relative activities of meizothrombins". United States.
@article{osti_6718609,
title = {Multiple active forms of thrombin. IV. Relative activities of meizothrombins},
author = {Doyle, M F and Mann, K G},
abstractNote = {The prothrombin activation intermediates meizothrombin and meizothrombin(desF1) (meizothrombin that has been autoproteolyzed to remove fragment 1) have been obtained in a relatively pure, active form with minimal autolysis, making them suitable for enzymatic characterization. When compared at equimolar concentrations, alpha-thrombin, fragment 1.2+ alpha-thrombin, meizothrombin(desF1), and meizothrombin have approximately 100, 100, 10, and 1% activity, respectively, toward the macromolecular substrates factor V, fibrinogen, and platelets. The difference in activity of these four enzymes cannot be attributed to alterations in the catalytic triad, as all four enzymes have nearly identical catalytic efficiency toward the chromogenic substrate S2238. Further, the ability of meizothrombin and meizothrombin(desF1) to activate protein C was 75% of the activity exhibited by alpha-thrombin or fragment 1.2+ alpha-thrombin. All four enzymes bind to thrombomodulin, as judged by the enhanced rate of protein C activation upon preincubation of the enzymes with thrombomodulin. The extent of rate enhancement varied, with meizothrombin/thrombomodulin exhibiting only 50% of the alpha-thrombin/thrombomodulin rate. This difference in rate is not due to a decreased affinity of the meizothrombin for thrombomodulin since the apparent dissociation constants for the alpha-thrombin-thrombomodulin complex and the meizothrombin-thrombomodulin complex are virtually identical. The difference in the observed rate is due in part to the higher Km for protein C exhibited by the meizothrombin-thrombomodulin complex. Incubation of the thrombomodulin-enzyme complex with phospholipid vesicles caused an increase in the protein C activation rates. The kinetic constants for protein C activation in the presence of phospholipid are virtually identical for these enzyme-thrombomodulin complexes.},
doi = {},
url = {https://www.osti.gov/biblio/6718609}, journal = {Journal of Biological Chemistry; (USA)},
issn = {0021-9258},
number = ,
volume = 265:18,
place = {United States},
year = {1990},
month = {6}
}