There is a high functional diversity within the structural superfamily of porphyrin-binding dimeric α + β barrel proteins. In this review we aim to analyze structural constraints of chlorite dismutases, dye-decolorizing peroxidases and coproheme decarboxylases in detail. We identify regions of structural variations within the highly conserved fold, which are most likely crucial for functional specificities. The loop linking the two ferredoxin-like domains within one subunit can be of different sequence lengths and can adopt various structural conformations, consequently defining the shape of the substrate channels and the respective active site architectures. The redox cofactor, heme b or coproheme, is oriented differently in either of the analyzed enzymes. By thoroughly dissecting available structures and discussing all available results in the context of the respective functional mechanisms of each of these redox-active enzymes, we highlight unsolved mechanistic questions in order to spark future research in this field.

在卟啉结合二聚体 α + β 桶状蛋白的结构超家族中存在高度的功能多样性。在这篇综述中，我们旨在详细分析亚氯酸盐歧化酶、染料脱色过氧化物酶和粪血红素脱羧酶的结构限制。我们确定了高度保守折叠内的结构变异区域，这很可能对功能特异性至关重要。在一个亚基内连接两个类铁氧还蛋白结构域的环可以具有不同的序列长度，并且可以采用各种结构构象，从而确定底物通道的形状和各自的活性位点结构。氧化还原辅助因子，血红素b或coproheme，在任何一种分析的酶中都有不同的取向。通过彻底剖析可用结构并在这些氧化还原活性酶各自功能机制的背景下讨论所有可用结果，我们突出了未解决的机制问题，以激发该领域的未来研究。