. Author manuscript; available in PMC: 2019 Mar 14.

Published in final edited form as: Chem Rev. 2018 Feb 5;118(5):2554–2592. doi: 10.1021/acs.chemrev.7b00457

Table 1. Nonheme Diiron Enzymes Involved in Dioxygen Activation.

protein	function or reaction catalyzed	protein fold	notable organisms	refs
hemerythrin (Hr)	reversible dioxygen binding in invertebrates	4-helix bundle	Phascolopsis gouldii, Themiste zostericola	18–22
soluble methane monooxygenase hydroxylase (sMMOH)	conversion of methane to methanol in methanotrophs	4-helix bundle	Methylosinus trichosporium OB3b, Methylococcus capsulatus (Bath)	23–36
ribonucleotide reductase R2 protein from E. coli (RNR-R2)	conversion of ribonucleotides to deoxyribonucleotides	4-helix bundle	Escherichia coli	37–44
stearoyl acyl carrier protein (ACP) Δ⁹-desaturase (Δ⁹D)	conversion of stearoyl-ACP to oleyl-ACP in plants	4-helix bundle	Ricinus communis	45–49
ferroxidase site of frog M ferritin	oxidation of Fe(II) to Fe(III) prior to biomineralization	4-helix bundle	Rana catesbeiana	50–53
toluene/o-xylene monooxygenase hydroxylase (ToMOH)	hydroxylation of toluene and o-xylene in bacteria	4-helix bundle	Pseudomonas stutzeri	24,54–56
toluene 4-monooxygenase hydroxylase (T4MOH)	hydroxylation of toluene to p-cresol in bacteria	4-helix bundle	Pseudomonas mendocina	14,28,57
aldehyde deformylating oxygenase (ADO)	conversion of fatty aldehydes to formate and alkanes	4-helix bundle	Nostoc punctiforme	58,59
AurF	p-aminobenzoate N-oxygenase in the biosynthesis of aureothin	4-helix bundle	Streptomyces thioluteus	8,60–62
CmlI	arylamine N-oxygenase in chloramphenicol biosynthesis	4-helix bundle	Streptomyces venezuelae	9,63,64
CmlA	β-hydroxylation of p-amino-phenylalanine in the first step of chloramphenicol biosynthesis	metallo-β-lactamase	Streptomyces venezuelae	12,65,66
human deoxyhypusine hydroxylase (hDOHH)	hydroxylation of deoxyhypusine residue on the eukaryotic initiation factor 5a that controls cell proliferation	HEAT repeat	Homo sapiens	67,68