Oxidative inactivation of plasmin and other serine proteases by copper and ascorbate

Fibrin thrombi form at sites of injury, where leukocytes release a variety of oxidants. To determine whether oxidants might affect proteins of the fibrinolytic system, we examined the effects of various oxidants on plasmin. Plasmin was not inhibited by micromolar concentrations of hypochlorous acid, chloramine T, or H2O2. Neither Fe nor Cu affected plasmin alone or in the presence of H2O2. However, incubation of plasmin with 5 mumol/L Cu(I or II) in the presence of the reducing agent ascorbic acid resulted in a loss of its hydrolytic activity towards proteins as well as towards small synthetic substrates. The addition of EDTA, but not mannitol, prevented its inactivation. Inactivation was prevented by the addition of catalase and accelerated by hydrogen peroxide. Preincubation of plasmin with the competitive inhibitor alpha-N-acetyl-L-lysine methyl ester prevented inactivation by Cu(II) and ascorbate. These results together suggest site-specific oxidation of plasmin's active site. Treatment of the plasminogen activators tissue plasminogen activator and two-chain urokinase-type plasminogen activator, as well as trypsin, neutrophil elastase, and thrombin with Cu(II) and ascorbate resulted in a loss of their amidolytic and proteolytic activity, indicating the general susceptibility of serine proteases to this type of oxidation. Oxidation of the zymogens Glu-plasminogen and single-chain urokinase-type plasminogen activator by Cu(II) and ascorbate resulted in the failure of these molecules to generate active enzymes when treated with plasminogen activators or plasmin, respectively. The active site His residue may be the target of oxidative inactivation, as evidenced by the partial protection afforded plasmin by the addition of Zn(II), histidine, or the platinum derivative, platinum(II) (2,2':6',2"- terpyridine) chloride. Because platelets contain micromolar concentrations of Cu and leukocytes are rich in ascorbate, Cu-dependent site-specific oxidation might play a role in modulating proteolytic events and the life span of thrombi formed at sites of tissue injury.     

超声造影检测心肌梗死患者受损左室壁的价值

目的探讨超声造影在检测心肌梗死患者左室壁受损范围中的价值。方法对75名发生心肌梗死的患者进行实时心肌造影,分别于超声造影前后观察心内膜边界显示情况,评价和比较节段室壁运动情况。结果超声造影后左室心内膜边界的显示较造影前明显清晰,受损节段与未受损节段的对比增强。以冠状动脉造影结果为标准,造影检测的灵敏度、特异度和准确度均高于造影前（p〈0．05）。结论实时超声造影能有效增强左室心内膜边界显示和受损心肌边界显影,提高对左室壁受损范围检测的准确性。     

Protein co-isolated with human tissue factor impairs recovery of activity

Preparations of human tissue factor isolated by immunoaffinity chromatography contain variable amounts of 47,000 mol wt, 55,000 mol wt, and multimeric tissue factor when analyzed without reduction on polyacrylamide gels in sodium dodecyl sulfate (SDS). When analyzed after reduction, the 47,000 mol wt tissue factor apoprotein and a protein of about 12,000 mol wt are observed. Elution of tissue factor from polyacrylamide gel slices, followed by reassociation with lipids, restored proportionately much greater tissue factor activity with the 47,000-mol wt protein than with the 55,000-mol wt form. Cyanogen bromide cleavage at the single tissue factor methionine revealed that the 12,000-mol wt protein is associated with the carboxyl-terminal peptide derived from the 47,000-mol wt protein. These results reveal that association of the 12,000-mol wt protein with the cytoplasmic domain of tissue factor can modulate its activity in vitro.