Kashiwagi A, Kashiwagi K, Takase M, Hanada H, Yamashita M, Naitoh T, Nakamura M
Laboratory for Amphibian Biology, Faculty of Science, Hiroshima University, Japan.
Comp Biochem Physiol B Biochem Mol Biol. 1998 Jan;119(1):235-9. doi: 10.1016/s0305-0491(97)00321-0.
The authors succeeded in raising a single mature haploid Rana rugosa female to the age of 2 years from an egg artificially fertilized with ultraviolet-irradiated sperm. In order to discover why this particular haploid individual should survive so long, hydrogen peroxide detoxifying catalase in the liver of this individual and age-matched diploids was examined and compared for total activity, temperature stability, and chemical inhibition. Total activity was found to be significantly higher in the haploid frog than in the diploids, suggesting that this particular haploid had a unique system for hydrogen peroxide detoxification which protected the liver against cell death, preventing hepatic failure, and leading to a prolonged survival. Liver catalase from the haploid proved to be more labile to aminotriazole and urea, losing 60-70% of its original activity after 30 min treatment, whereas diploid catalase lost only 40% under the same conditions. Haploid and diploid catalase responded similarly to heat, however. It seems likely that inhibitor-binding sites differ considerably between the catalase of normal diploids and the catalase of this particular haploid, while overall structure is generally similar.
作者成功地将一只由紫外线照射过的精子人工授精的卵发育而来的成熟单倍体日本皱蛙雌性饲养到了2岁。为了探究为何这个特定的单倍体个体能存活如此之久，研究人员检测并比较了该个体及年龄匹配的二倍体个体肝脏中过氧化氢解毒酶——过氧化氢酶的总活性、温度稳定性和化学抑制情况。结果发现，单倍体青蛙肝脏中过氧化氢酶的总活性显著高于二倍体，这表明这个特定的单倍体拥有独特的过氧化氢解毒系统，该系统可保护肝脏免受细胞死亡的影响，防止肝衰竭，从而延长生存期。研究还发现，单倍体青蛙肝脏中的过氧化氢酶对氨基三唑和尿素更为敏感，处理30分钟后其原始活性丧失60 - 70%，而在相同条件下二倍体青蛙肝脏中的过氧化氢酶仅丧失40%的活性。不过，单倍体和二倍体的过氧化氢酶对热的反应相似。正常二倍体的过氧化氢酶与这个特定单倍体的过氧化氢酶之间，抑制剂结合位点可能存在显著差异，而总体结构通常相似。
