Essential amino acid residues controlling the unique regioselectivity of heme oxygenase in Pseudomonas aeruginosa
Essential amino acid residues controlling the unique regioselectivity of heme oxygenase in Pseudomonas aeruginosa
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DOI：
10.1021/ja031791i
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发表时间：
2004-04-14
影响因子：
15
通讯作者：
Yoshida, T
中科院分区：
文献类型：
--
作者：
Fujii, H;Zhang, XH;Yoshida, T
血红素加氧酶（HO）是一种两亲性微粒体蛋白，催化血红素（铁-原卟啉IX）氧化降解为α-胆绿素、CO和游离铁离子。有趣的是，所有HO区域特异性地氧化血红素的α-内消旋位置以形成α-胆绿素异构体，而非酶促血红素降解以几乎相同的产率形成所有四种可能的α-、β-、γ-、δ-胆绿素异构体。最近，在革兰氏阴性菌铜绿假单胞菌的HO（PigA）中发现了一个有趣的例子，它根本不产生α-胆绿素，而是形成β-胆绿素和γ-胆绿素的混合物，比例为3：7。在研究PigA独特的区域选择性的机制时，我们发现必需氨基酸残基Lys 34、Lys 132和Phe 189控制PigA独特的区域选择性。在这篇文章中，我们发现Lys 34和Lys 132是通过与血红素丙酸酯的氢键相互作用将旋转血红素保持在PigA活性位点的必需氨基酸残基，并且Phe 189通过与血红素取代基的空间相互作用控制β-和δ-胆绿素的产物比例。这些相互作用将血红素的β-或δ-内消旋位置置于PigA的氧化位点，导致独特的区域选择性。
Heme oxygenase (HO), an amphipathic microsomal protein, catalyzes the oxygen-dependent degradation of heme (iron-protoporphyrinIX) to α-biliverdin, CO, and free iron ion. Interestingly, all of HO regiospecifically oxidize the α-meso position of the heme to form α-biliverdin isomer while nonenzymatic heme degradation forms all four possible α-, β-, γ-, δ-biliverdin isomers at nearly identical yield. Recently, an interesting example has been found in HO (PigA) of the Gram-negative bacteriumPseudomonas aeruginosa, which does not produce α-biliverdin at all, but forms the mixture of β- and γ-biliverdins at a ratio of 3:7. While studying the mechanism of the unique regioselectivty of PigA, we found essential amino acid residues, Lys34, Lys132, and Phe189, controlling the unique regioselectivity of PigA. In this communication, we show that Lys34 and Lys132 are essential amino acid residues to hold the rotated heme in the active site of PigA via hydrogen-bonding interaction with the heme propionate and that Phe189 controls the product ratio of β- and δ-biliverdins via steric interaction with heme substituents. These interactions place the β- or δ-meso position of the heme at the oxidation site of PigA, leading to the unique regioselectivity.