期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 104, 期 12, 页码 5079-5084出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0700547104
关键词
heme; porphyrins; iron; oxidation
资金
- NCRR NIH HHS [M01 RR00064, M01 RR000064] Funding Source: Medline
- NIDDK NIH HHS [R01 DK20503, R01 DK020503, P30 DK072437] Funding Source: Medline
- NIGMS NIH HHS [R01 GM856775] Funding Source: Medline
Porphyria cutanea tarda (PCT), the most common form of porphyria in humans, is due to reduced activity of uroporphyrinogen decarboxylase (URO-D) in the liver. Previous studies have demonstrated that protein levels of URO-D do not change when catalytic activity is reduced, suggesting that an inhibitor of URO-D is generated in hepatocytes. Here, we describe the identification and characterization of an inhibitor of LIRO-D in liver cytosolic extracts from two murine models of PCT: wild-type mice treated with iron, 8-aminolevulinic acid, and polychlorinated biphenyls; and mice with one null allele of Uro-d and two null alleles of the hemochromatosis gene (Uro-d(+/-), Hfe(-/-)) that develop PCT with no treatments. in both models, we identified an inhibitor of recombinant human URO-D (rhURO-D). The inhibitor was characterized by solid-phase extraction, chromatography, UV-visible spectroscopy, and mass spectroscopy and proved to be uroporphomethene, a compound in which one bridge carbon in the uroporphyrinogen macrocycle is oxidized. We synthesized uroporphomethene by photooxidation of enzymatically generated uroporphyrinogen I or Ill. Both uroporphomethenes inhibited rhURO-D, but the Ill isomer porphomethene was a more potent inhibitor. Finally, we detected an inhibitor of rhURO-D in cytosolic extracts of liver biopsy samples of patients with PCT. These studies define the mechanism underlying clinical expression of the PCT phenotype, namely oxidation of uroporphyrinogen to uroporphomethene, a competitive inhibitor of URO-D. The oxidation reaction is iron-dependent.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据