Iron Cofactors: Nonhaem

Abstract

Abstract Proteins and enzymes with nonhaem iron centres display many functions: metal centres with primarily sulfur ligation are involved in electron transfer, electrophilic activation of hydroxyl groups, fixation of N 2 and regulation of gene expression; mononuclear and diiron centres with oxygen and nitrogen ligation have roles in various reactions with O 2 and in hydrolysis. The principles of their mechanisms of action have emerged from considerable experimentation. Ongoing research is refining understanding of their mechanisms of action and attempting to test and extend their already substantial catalytic capabilities. Key Concepts Nonhaem iron‐containing enzymes carry out a myriad of catalytic reactions. Iron–sulfur centres participate in electron transfer, electrophilic catalysis, nitrogenase and hydrogenase reactions. Mononuclear and diiron monooxygenases, dioxygenases and oxidases provide nonhaem counterparts to catalysis carried out by haem‐containing enzymes. Rearrangements of protein ligands in nonhaem iron active sites provide a unique aspect to control catalysis. Nonhaem oxidative enzymes access high‐valent states of iron during catalysis. The electrophilic nature of nonhaem iron also supports effective hydrolytic catalysis in reactions where O 2 activation is not required.