Onuki J, Medeiros M H, Bechara E J, Di Mascio P
Departamento de Bioquímica, Universidade de São Paulo, Brazil.
Biochim Biophys Acta. 1994 Feb 22;1225(3):259-63. doi: 10.1016/0925-4439(94)90004-3.
5-Aminolevulinic acid (ALA), a heme precursor accumulated in chemical and inborn porphyrias, has been demonstrated to produce reactive oxygen species upon metal-catalyzed aerobic oxidation and to cause oxidative damage to proteins, liposomes and subcellular structures. Exposure of plasmid pBR322 DNA to ALA (0.01-3 mM) in the presence of 10 microM Fe2+ ions causes DNA single-strand breaks (ssb), revealed by agarose gel electrophoresis as an increase in the proportion of the open circular form (75 +/- 7.5% at 3 mM ALA) at the expense of the supercoiled form. Addition of either anti-oxidant enzymes such as superoxide dismutase (10 micrograms/ml) and catalase (20 micrograms/ml), or a metal chelator (DTPA, 2.5 mM), or a HO. scavenger (mannitol, 100 mM) inhibited the damage (by 30, 45, 55, and 81%, respectively), evidencing the involvement of O2-., H2O2 and HO. (by the Haber-Weiss reaction) in this process. Hydrogen peroxide (100 microM) or Fe2+ (10 microM) alone were of little effect on the extent of DNA ssb. The present data may shed light on the correlation reported between primary liver-cell carcinoma and intermittent acute porphyria.
5-氨基乙酰丙酸（ALA）是化学性和先天性卟啉症中积累的血红素前体，已证明其在金属催化的需氧氧化过程中会产生活性氧，并对蛋白质、脂质体和亚细胞结构造成氧化损伤。在10微摩尔Fe2+离子存在的情况下，将质粒pBR322 DNA暴露于ALA（0.01 - 3毫摩尔）会导致DNA单链断裂（ssb），琼脂糖凝胶电泳显示为开环形式的比例增加（在3毫摩尔ALA时为75±7.5%），超螺旋形式减少。添加抗氧化酶如超氧化物歧化酶（10微克/毫升）和过氧化氢酶（20微克/毫升）、金属螯合剂（二乙烯三胺五乙酸，DTPA，2.5毫摩尔）或羟基自由基清除剂（甘露醇，100毫摩尔）均可抑制损伤（分别抑制30%、45%、55%和81%），证明超氧阴离子、过氧化氢和羟基自由基（通过哈伯-维伊斯反应）参与了这一过程。单独的过氧化氢（100微摩尔）或Fe2+（10微摩尔）对DNA单链断裂程度影响很小。目前的数据可能有助于阐明原发性肝细胞癌与间歇性急性卟啉症之间报道的相关性。
