Evans M J, Eddy M, Plummer J
J Biol Chem. 1985 Jan 10;260(1):306-14.
An apparently unique isozyme of lactate dehydrogenase has been reported associated with transformation by Kirsten sarcoma virus, which was also expressed in human cancer. This isozyme was designated LDHk (Anderson, G.R., and Kovacik, W.P., Jr., (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 3209-3213; Anderson, G. R., Kovacik, W. P., Jr., and Marotti, K. R. (1981) J. Biol. Chem. 256, 10583-10591). However, preparations of LDH5 from human placenta and from HeLa cells were later shown to exhibit some of the properties ascribed to LDHk9 and the identify of LDHk as a unique isozyme was questioned (Morin, M. E., and Hance, A. J., (1983) J. Biol. Chem. 258, 2864-2869). Saavadra and Anderson (Saavedra, R. A., and Anderson, G. R. (1983) Science (Wash. D.C.) 221, 291-292) refuted the arguments of Morin and Hance (Morin, M. E., and Hance, A. J. (1983) J. Biol. Chem. 258, 2864-2869) by claiming that commercial preparations of human placental LDH5 were contaminated with LDHk. Re-evaluation of the unique properties which distinguish LDHk from conventional LDH5 indicates that the two isozymes may not be different. Highly purified preparations of LDHk exhibit a single Mr = 34,000 polypeptide subunit on sodium dodecyl sulfate-acrylamide gels, yet retain activity detectable as both LDHk and LDH5. Attempts to separate LDHk and LDH5 by column chromatography or by continuous electrophoresis on a variety of solid support matrices were unsuccessful. Enzyme activity identified as LDHk in imidazole-borate-buffered gels migrating toward the cathode was detected as LDH5 activity on re-electrophoresis. LDH5 activity identified by electrophoretic migration toward the anode in Tris-glycine-buffered gels also recorded as LDHk when re-electrophoresed toward the cathode in imidazole-borate-buffered gels. Quantitative assays of enzyme activity recovered from the two-gel assay systems, as well as re-electrophoresis of isozyme-enriched preparations, indicated that cross-contamination of isozymes was not responsible for the results obtained.
据报道，一种明显独特的乳酸脱氢酶同工酶与 Kirsten 肉瘤病毒介导的转化有关，该同工酶也在人类癌症中表达。这种同工酶被命名为 LDHk（安德森，G.R.，和科瓦西克，W.P.，Jr.，（1981 年）《美国国家科学院院刊》78 卷，3209 - 3213 页；安德森，G.R.，科瓦西克，W.P.，Jr.，和马罗蒂，K.R.（1981 年）《生物化学杂志》256 卷，10583 - 10591 页）。然而，后来发现从人胎盘和 HeLa 细胞中制备的 LDH5 制剂表现出一些归因于 LDHk 的特性，因此 LDHk 作为一种独特同工酶的身份受到质疑（莫林，M.E.，和汉斯，A.J.，（1983 年）《生物化学杂志》258 卷，2864 - 2869 页）。萨瓦德拉和安德森（萨瓦德拉，R.A.，和安德森，G.R.（1983 年）《科学》（华盛顿特区）221 卷，291 - 292 页）反驳了莫林和汉斯的观点（莫林，M.E.，和汉斯，A.J.（1983 年）《生物化学杂志》258 卷，2864 - 2869 页），声称人胎盘 LDH5 的商业制剂被 LDHk 污染。对区分 LDHk 与传统 LDH5 的独特特性进行重新评估表明，这两种同工酶可能并无差异。在十二烷基硫酸钠 - 丙烯酰胺凝胶上，高度纯化的 LDHk 制剂显示出单一的 Mr = 34,000 多肽亚基，但仍保留可检测到的 LDHk 和 LDH5 活性。试图通过柱色谱法或在各种固体支持基质上进行连续电泳来分离 LDHk 和 LDH5 均未成功。在咪唑 - 硼酸盐缓冲凝胶中向阴极迁移时被鉴定为 LDHk 的酶活性，在重新电泳时被检测为 LDH5 活性。在 Tris - 甘氨酸缓冲凝胶中向阳极电泳迁移时鉴定的 LDH5 活性，当在咪唑 - 硼酸盐缓冲凝胶中向阴极重新电泳时也记录为 LDHk。从双凝胶分析系统中回收的酶活性的定量测定，以及同工酶富集制剂的重新电泳，表明同工酶的交叉污染并非所获结果的原因。
