Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.7 (plasmin)
 9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Addition of enzymatically active 125-I-labeled C1s (the esterase which is part of the activated complex protein of serum designated as the first component of complement or C1) to purified C4 (the naturally occurring fourth component of human serum complement) results in binding of a portion of the C1s to C4 as indicated by sucrose density gradient ultracentrifugation. Demonstration of binding requires hemolytically active C4, but not enzymatically active C1s. The latter was demonstrated by using DFP inactivated C1s as well as fragments of C1s produced by prior protease treatment of the C1s. While treatment of C1s with proteases (human leukocyte lysosomal enzymes, trypsin or plasmin) resulted in progressive inactivation of the enzymatic activity, the decline in esteratic activity occurred at a much slower rate than the decline in functional activity (inactivation of C4 in free solution). The data lead to the probable conclusion that C1s contains an enzymatic (or esteratic) site in addition to a binding site. The latter might be important for positioning a large molecule, such as C4, in order to effect proteolytic cleavage at the proper bond and hence prepare C4 to participate in the complement sequence.
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PMID:Interaction of C1s and C4. A binding phenomenon. 12 5

In isolated rabbit lungs standardized amounts of edema were induced. Stimulation with the Ca ionophore A23187, leukotriene C4, Pseudomonas aeruginosa cytotoxin and human serum (activated complement) all resulted in protein leakage into the alveolar space with no change in the total phospholipid content. The pressure-volume characteristics of the lungs and the characteristics of the lavage surfactant (Wilhelmy balance) were markedly altered, correlating to the lavage protein content. The surfactant alterations were reproduced by addition of perfusion fluid protein to control surfactant in vitro. All changes were far less expressed or even missing in isolated lungs developing the same amount of edema due to omittance of proteins from the perfusion liquid. Different proteins added to control surfactant in the Wilhelmy balance showed a marked rank order of potency in interfering with surfactant function: immunoglobulins G and M and elastin less than albumin less than fibrinogen less than fibrin monomers. The fibrin monomer effect was reproduced by addition of thrombin to a surfactant fibrinogen mixture and was partly reversed by subsequent incubation with plasmin. In conclusion, high-permeability edema induced by different means results in alterations of lung mechanics and surface activity of lavaged surfactant, presumably due to protein surfactant interaction. Among different proteins, fibrin monomers are especially effective in interfering with surfactant function.
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PMID:Alteration of surfactant function due to protein leakage: special interaction with fibrin monomer. 383 43