Willems J, Zwijsen A, Slegers H, Nicolaï S, Bettadapura J, Raymackers J, Scarcez T
Interdisciplinary Research Center, KULAK, Kortrijk, Belgium.
J Biol Chem. 1993 Nov 25;268(33):24614-21.
An enzyme which converts radical oxygen, produced by phorbol 12-myristate 13-acetate activated neutrophils, into nonluminescent products is secreted by rat C6 glioma. The enzyme was purified from chemically defined conditioned media and identified as an extracellular superoxide dismutase (EC-SOD). The purified enzyme is distinct from human EC-SOD C (Hjalmarsson, K., Marklund, S. L., Engström, A., and Edlund, T. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 6340-6344) by its elution from heparin-Sepharose at 300-400 mM NaCl, its pI of 6.1-7.2, and its native M(r) of 85,000 +/- 20,000. The rat EC-SOD is a dimer with a subunit M(r) of 34,000-36,000 and is extensively modified by post-translational processing. Although rat EC-SOD has a high sequence homology with the catalytic center and the polybasic heparin-binding site near the COOH terminus of human EC-SOD C, its NH2-terminal sequence and the sequences flanking the heparin-binding site differ substantially. The sequence of the isolated rat EC-SOD cDNA fully confirms the data obtained from amino acid sequence analysis. The amino acid sequence of the enzyme and its biochemical properties support its identification as the rat EC-SOD B.
大鼠C6胶质瘤分泌一种酶，该酶可将佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯激活的中性粒细胞产生的活性氧转化为非发光产物。该酶从化学成分明确的条件培养基中纯化得到，被鉴定为细胞外超氧化物歧化酶（EC - SOD）。纯化后的酶与人类EC - SOD C（Hjalmarsson, K., Marklund, S. L., Engström, A., and Edlund, T. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 6340 - 6344）不同，其在300 - 400 mM NaCl浓度下从肝素 - 琼脂糖上洗脱，其pI为6.1 - 7.2，天然M(r)为85,000 ± 20,000。大鼠EC - SOD是一种二聚体，亚基M(r)为34,000 - 36,000，并且经过广泛的翻译后加工修饰。尽管大鼠EC - SOD与人类EC - SOD C的催化中心以及COOH末端附近的多碱性肝素结合位点具有高度的序列同源性，但其NH2末端序列以及肝素结合位点两侧的序列有很大差异。分离得到的大鼠EC - SOD cDNA序列完全证实了从氨基酸序列分析获得的数据。该酶的氨基酸序列及其生化特性支持将其鉴定为大鼠EC - SOD B。
