Understanding molecular enzymology of porphyrin-binding alpha plus beta barrel proteins - One fold, multiple functions

There is a high functional diversity within the structural superfamily of porphyrin-binding dimeric alpha + beta 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.

Automated summary

This review focuses on the high functional diversity within the structural superfamily of porphyrin-binding dimeric alpha + beta barrel proteins, specifically analyzing chlorite dismutases, dye-decolorizing peroxidases, and coproheme decarboxylases in detail. Differences in sequence lengths and structural conformations in loop regions connecting ferredoxin-like domains within subunits contribute to defining substrate channels and active site architectures. The orientation of the redox cofactor varies in the analyzed enzymes, highlighting unsolved mechanistic questions and suggesting areas for future research.