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PHOTOCOAGULATION OF HUMAN PLASMA: ACYL SERINE PROTEINASE PHOTOCHEMISTRY
Author(s) -
Porter Ned A.,
Bruhnke John D.
Publication year - 1990
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1990.tb01681.x
Subject(s) - thrombin , chemistry , photodissociation , serine , enzyme , coagulation , serine protease , biochemistry , human plasma , photochemistry , chromatography , biology , platelet , protease , psychology , psychiatry , immunology
— Human a‐thrombin or bovine Factor Xa was acylated at the active site serine hydroxy! with a‐methyl‐2‐hydroxy‐4‐diethylaminocinnamic acid. These modifed serine proteinase enzymes showed no plasma coagulation biological activity in the absence of light. Photolysis of the acyl serine proteinase enzymes in plasma for1–35 s with monochromatic 366 nm light isolated from a high pressure mercury arc results in coagulation of the plasma. For example, photolysis of 3 NIH U of the acyl human a‐thrombin for 5 s in human plasma results in a clot in 23 s. For comparison, 1 NIH U of unmodified human a‐thrombin gave a clot in 21 s under the conditions of the assay but without photolysis. Appropriate controls showed that the coagulation is the result of the formation of active thrombin due to photodeacylation of the enzymes. The photoinduced clotting time measured is dependent on acyl thrombin concentration and photolysis time. Thus higher concentrations of acyl thrombin and longer photolysis times give a shorter clotting time. A kinetic scheme based upon Lineweaver‐Burke analysis of the clotting process is developed.