Document Detail

Denatured proteins as cofactors for plasminogen activation.
MedLine Citation:
PMID:  9264548     Owner:  NLM     Status:  MEDLINE    
Activation of covalently intact plasminogen by tissue-type plasminogen activator (tPA) is facilitated by a majority of proteins subjected to denaturing conditions. Except for heat-denatured apoferritin, the denatured proteins examined require partial proteolysis by plasmin for cofactor activity. The same proteins in their native state are resistant to proteolysis with plasmin and develop no activity. Denatured preparations of apoferritin, antithrombin, alpha1-protease inhibitor, alpha2-macroglobulin, and albumin also accelerate des(1-77)-plasminogen activation by tPA. The rate enhancements are comparable with that of the fibrin(ogen) fragments on a w/w basis. The cofactor activities are inhibited by 6-aminohexanoate and inactivated by pepsin. Analysis of heat-denatured apoferritin and albumin preparations by ultracentrifugation and gel chromatography indicates that cofactor is associated predominately with aggregates, which have binding capacity for both tPA and zymogen. Heat-denatured albumin pretreated with plasmin decreases K(M) and increases k(cat) for both intact plasminogen and des(1-77)-plasminogen activation by tPA, yielding catalytic efficiencies in excess of 8 x 10(3) M(-1) s(-1) and 2 x 10(4) M(-1) s(-1), respectively. Because of enhanced plasmin-catalyzed proteolysis of plasminogen to des(1-77)-plasminogen, activation by urokinase-type plasminogen activator is also facilitated by denatured proteins; activation of des(1-77)-plasminogen is not affected. It is concluded that denatured proteins serve as both cofactors and substrates in the fibrinolytic system, and that enhancement of plasminogen activation by denatured proteins is mechanistically indistinguishable from that observed with fibrin.
R Machovich; W G Owen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Archives of biochemistry and biophysics     Volume:  344     ISSN:  0003-9861     ISO Abbreviation:  Arch. Biochem. Biophys.     Publication Date:  1997 Aug 
Date Detail:
Created Date:  1997-09-08     Completed Date:  1997-09-08     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  0372430     Medline TA:  Arch Biochem Biophys     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  343-9     Citation Subset:  IM    
Department of Biochemistry and Molecular Biology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
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MeSH Terms
Apoferritins / metabolism
Blood Proteins / metabolism*
Electrophoresis, Polyacrylamide Gel
Enzyme Activation / physiology
Fibrinolysin / metabolism
Peptide Fragments / metabolism
Plasminogen / metabolism*
Protein Denaturation*
Serum Albumin / metabolism
Tissue Plasminogen Activator / metabolism*
Urokinase-Type Plasminogen Activator / metabolism
Grant Support
Reg. No./Substance:
0/Blood Proteins; 0/Peptide Fragments; 0/Serum Albumin; 9001-91-6/Plasminogen; 9013-31-4/Apoferritins; EC Plasminogen Activator; EC; EC Plasminogen Activator

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