Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fibrinolytic studies in euglobulin fractions of Fletcher trait plasma (deficient in prekallikrein) revealed reduced activities as compared to normal plasma. A quantitative assay for total plasminogen activator plus proactivator in plasma showed that the amount in Fletcher trait patients is about half of normal (normal = +/- 100 blood activator units [BAU]/ml). Plasma kallikrein partially purified in a high and low molecular weight form exerted plasminogen activator activity amounting to 10-15 BAU/ml plasma. So, the absence of kallikrein in the deficient plasma cannot fully account for the reduction in activator activity. Additions of kallikrein preparations or normal plasma fractions resulted in additional activator activity in Fletcher trait plasma which was assessed at 30-40 BAU/ml. This activity was assumed to originate from a previously undescribed plasminogen proactivator whose activation is kallikrein- and factor XII-dependent. Fractionation experiments demonstrated the presence of two major activities and a minor activity caused by kallikrein in normal plasma. It is concluded that plasma kallikrein has two functions in the generation of factor XII-dependent fibrinolytic activity: one as a direct plasminogen activator and another as a factor in the activation of a major factor XII-dependent plasminogen proactivator.
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PMID:Factor XII-dependent fibrinolysis: a double function of plasma kallikrein and the occurrence of a previously undescribed factor XII- and kallikrein-dependent plasminogen proactivator. 48 48

The conversion of plasminogen proactivator to plasminogen activator by Hageman factor fragments results in the generation of chemotactic activity for human neutrophils. This chemotactic activity can be distinguished from that generated by Hageman factor activation of prekallikrein and is demonstrable in plasma that is genetically deficient in prekallikrein (Fletcher factor deficiency). Both the plasminogen-activating activity and chemotactic activity produced by the interaction of Hageman factor fragments and plasminogen proactivator to yield plasminogen activator were inhibited by diisopropyl fluorophosphate (DFP) indicating an essential role for the enzymatic site in both these activities. The finding that the plasminogen proactivator tolerated a dose of DFP, which completely inactivated the plasminogen activator, reveals that the active site is protected in the precursor protein.
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PMID:The fibrinolytic pathway of human plasma. II. The generation of chemotactic activity by activation of plasminogen proactivator. 472 52

Fibrinolytic studies in gamma G fractions of three Fletcher factor-deficient plasmas (functionally deficient in prekallikrein) revealed weak or no factor XII-independent activator activity. Two of the three Fletcher trait patients showed no plasminogen activator activity in clot lysis, fibrin plate, and amidolytic assays. The third patient showed no activator activity as determined by clot lysis and amidolytic assays but gave 10% of the activator activity detected in normal undiluted gamma G fraction in absence of HFf when determined by fibrin plate assay. Normal plasma gamma G fractions showed detectable and significant plasminogen activator activity. These fractions did not contain kallikrein or activated factor XI activities, thus indicating that the activator activity could not be attributed to the presence in these fractions or trace of these activated factors. Furthermore, factor XI-deficient plasma gamma G fraction, which was shown to contain no activated prekallikrein, showed normal plasminogen activator activity. Finally, specific antibodies to prekallikrein were shown not to quench the activity of plasminogen activator present in normal plasma gamma fraction. A double genetic deficiency to explain the absence in Fletcher factor-deficient plasma gamma G fractions of both prekallikrein proactivator and activator activities is not likely. Thus plasma prekallikrein, besides being a known plasminogen proactivator, appears to be required for the expression of a plasminogen activator activity.
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PMID:Factor XII-induced fibrinolysis. Diminished proactivator activity and drastic reduction of activator activity in Fletcher factor-deficient plasma gamma globulin. 618 61