Heme synthase (ferrochelatase) catalyzes the removal of iron from heme and demetalation of metalloporphyrins.
Heme synthase (ferrochelatase) catalyzes the removal of iron from heme and demetalation of metalloporphyrins.
复制标题
血红素合酶（铁螯合酶）催化血红素中铁的去除和金属卟啉的脱金属。
作者：
S. Taketani;Mutsumi Ishigaki;A. Mizutani;M. Uebayashi;M. Numata;Yoshiko Ohgari;S. Kitajima
肉制品（包括煮熟的腌火腿）中的红色素是由肌红蛋白与外源亚硝酸盐产生的一氧化氮反应产生的。由于用亚硝酸盐处理肉类可能会产生致癌的亚硝胺，因此生产不含亚硝酸盐的肉制品是一种有吸引力的替代方案。生干腌（帕尔马）火腿是用亚硝酸盐以外的盐处理肉类而制成的。对生干腌火腿中色素的分析表明，主要色素是原卟啉锌，这表明在生火腿加工过程中，血红素通过肌红蛋白血红素的除铁反应转化为锌原卟啉。除铁酶的纯化表明它与亚铁螯合酶相同。重组亚铁螯合酶与 NADH-细胞色素 b5 还原酶相结合，催化血红素和血红素蛋白中 NADH 依赖性除铁反应。金属离子如锌和钴也从相应的金属卟啉中去除。锌离子的添加导致锌原卟啉的形成。在培养的细胞中，观察到锌中卟啉向中血红素的转化依赖于亚铁螯合酶，并且可以在红系分化过程中被显着诱导。这是一种新酶反应的首次演示，即亚铁螯合酶的逆反应，这可能有助于开辟细胞内原卟啉和血红素回收的新途径。
The red pigments in meat products, including cooked cured ham, arise from the reaction of myoglobin with nitric oxide generated from exogenous nitrite. Since carcinogenic nitrosoamines may be generated by the treatment of meats with nitrite, the production of nitrite-free meat products is an attractive alternative. Raw dry-cured (Parma) hams are produced by the treatment of meats with salts other than nitrite. Analysis of pigments in raw dry-cured hams reveals that the main pigment is zinc protoporphyrin, suggesting that the conversion of heme to zinc protoporphyrin occurs via an iron-removal reaction from myoglobin heme during the processing of raw hams. Purification of the iron-removal enzyme showed that it was identical to ferrochelatase. Recombinant ferrochelatase in combination with NADH-cytochrome b5 reductase catalyzed NADH-dependent iron-removal reaction from hemin and hemoproteins. Metal ions such as zinc and cobalt were also removed from the corresponding metalloporphyrins. The addition of zinc ions led to the formation of zinc protoporphyrin. In cultured cells, the conversion of zinc mesoporphyrin to mesoheme was observed to be dependent on ferrochelatase and could be markedly induced during erythroid differentiation. This is the first demonstration of a new enzyme reaction, the reverse reaction of ferrochelatase, which may contribute to a new route of the recycling of protoporphyrin and heme in cells.