Azzo W, Woessner J F
J Biol Chem. 1986 Apr 25;261(12):5434-41.
A metalloprotease that digests cartilage proteoglycan optimally at pH 5.3 has been purified (4400-fold) to homogeneity from 20-g samples of human articular cartilage containing about 100 micrograms of enzyme. This enzyme was cleanly separated from a related neutral metalloprotease with an optimum pH of 7.2. The acid metalloprotease displays 40% of its maximum activity at pH 7.2 and so has significant activity at physiological pH. The protease is calcium-dependent and indirect evidence suggests that it may contain zinc at its active center. It occurs largely in a latent form that can be activated by aminophenylmercuric acetate. The apparent Mr of the latent form is 55,000 and of the active form, 35,000. The isoelectric point is at pH 4.9. The protease activity is inhibited by chelators, Z-phenylalanine, ovostatin, and tissue inhibitor of metalloproteinase from human articular cartilage. It differs from metalloproteinases such as enkephalinase and kidney brush-border protease in its failure to be strongly inhibited by phosphoramidon and Zincov. It cleaves the proteoglycan monomer of bovine nasal cartilage to fragments of approximately 140,000 Da. It cleaves the B chain of insulin at Ala14-Leu15 and Tyr16-Leu17. A survey of 26 cartilage extracts indicates this enzyme is elevated to about 3 times the normal level in human osteoarthritic cartilage and that the tissue inhibitor of metalloproteinase is only slightly diminished. Preliminary evidence points to the presence of a similar acid metalloprotease activity in human polymorphonuclear leukocytes.
一种在pH 5.3时能最佳消化软骨蛋白聚糖的金属蛋白酶已从20克含约100微克该酶的人关节软骨样品中纯化（纯化4400倍）至同质。该酶与一种最适pH为7.2的相关中性金属蛋白酶被清晰分离。酸性金属蛋白酶在pH 7.2时展现出其最大活性的40%，因此在生理pH下具有显著活性。该蛋白酶依赖钙，间接证据表明其活性中心可能含有锌。它主要以潜伏形式存在，可被氨基苯基汞乙酸激活。潜伏形式的表观分子量为55,000，活性形式为35,000。等电点在pH 4.9。蛋白酶活性受到螯合剂、Z - 苯丙氨酸、卵抑素以及人关节软骨金属蛋白酶组织抑制剂的抑制。它与脑啡肽酶和肾刷状缘蛋白酶等金属蛋白酶不同，不会被磷酰胺和锌诺强烈抑制。它将牛鼻软骨的蛋白聚糖单体切割成约140,000 Da的片段。它在Ala14 - Leu15和Tyr16 - Leu17处切割胰岛素的B链。对26种软骨提取物的调查表明，这种酶在人骨关节炎软骨中升高至正常水平的约3倍，而金属蛋白酶组织抑制剂仅略有减少。初步证据表明人多形核白细胞中存在类似的酸性金属蛋白酶活性。
