Macrophages and other phagocytes produce numerous pro teases (see Table 1), several of which can hydrolyze elastin, collagen, and other proteins present in the extracellular matrix. Although it is normal for small amounts of elastase and other proteinases leak into tissues throughout the body, their activities are normally kept in check by antiproteinases present in plasma and the extracellular fluid. One of these, α2-macroglobulin, attracts a wide range of pro teases with a “bait” region. Cleavage of a peptide bond in the bait region springs a conformational change that traps the pro tease responsible in a noncovalent complex with the antiproteinase, blocking further proteolytic assaults.

Disruption of the balance between proteases and anti-proteinases can have deleterious effects. For example, when inadequate drainage leads to the accumulation of large numbers of neutrophils, considerable tissue damage can result. In the lungs, a genetic defect that renders elastase insensitive to α1-antiproteinase inhibitor (α1-antitrypsin) and other antiproteinases contributes significantly to the pulmonary tissue damage associated with emphysema. The elevated levels of chlorinated oxidants such as HOCl associated with inflammation can activate several of the proteinases listed in Table 1, while simultaneously inactivating several counter vailing antiproteinases. In addition, these inhibitory proteins can themselves be degraded by proteases. For example, tissue inhibitor of metalloproteinases and α1-antichymotrypsin can be hydrolyzed by elastase while α1-antiproteinase inhibitor can be hydrolyzed by collagenase and gelatinase.

Table1. Enzymes & Proteins of the Granules of Phagocytic Leukocytes

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لتجنب ارتفاع سكر الدم.. ما أفضل وقت لتناول الحلوى؟

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مواضيع ذات صلة

Platelet Aggregation Requires Outside-In and Inside-Out Transmembrane Signaling

Phospholipid Bilayers Form a Sealed Compartment Surrounding an Internal Aqueous Space

Phospholipids Spontaneously Form Bilayers

Phagocytic Leukocytes Generate Reactive Oxygen Species During the Respiratory Burst

Leukocytes are Motile

Platelets

The Biochemical Basis of The ABO System

The Red Blood Cell Membrane

Oxidation of Heme Iron Compromises oxygen Transport

Hypervariable Regions Confer Binding Specificity

Immunoglobulins Are Comprised of Multiple Polypeptide Chains

Serum Inhibitors Prevent Indiscriminate Proteolysis