TABLE 1.

Summary of the known functions of radical SAM enzymes in methanogens and their distributions in different organisms^a

Radical SAM enzyme	Function(s)	Distribution(s)	Reference(s)
Tes	Tetraether lipid biosynthesis	Mostly archaea, some bacteria	22
PylB	Pyrrolysine biosynthesis	Methanosarcinales methanogens	32
MJ0619	Methylase in H4MPT biosynthesis	Methanogens and some bacteria	37
Mmp10	5-(S)-Methylarginine synthesis (posttranslational modification of MCR)	Methanogens	48, 50
QCMT	2-(S)-Methylglutamine synthesis (posttranslational modification of MCR)	Some methanogens	47
AhbC	Alternative heme biosynthesis, removal of 2 acetate side chains	Archaea and some bacteria	58
AhbD	Alternative heme biosynthesis, heme b synthase—conversion of 2 propionate side chains to vinyl groups	Archaea and some bacteria	58, 62
CofG/CofH	F0 synthase; F420 biosynthesis	Methanogens and some bacteria	71
NifB	Nitrogenase cofactor biosynthesis	Some archaea and some bacteria	74, 79
HcgA	[Fe]-hydrogenase cofactor biosynthesis	Hydrogenotrophic methanogens	89, 91
RaSEA	Archaeosine biosynthesis	Some archaea	102
Tyw1 (Taw1)	4-Demethylwyosine synthase; tRNA modification	Archaea and eukaryotes	108, 110
MtaB	ms2t6A tRNA modification	Widespread distribution in all domains of life	118
Elp3	cm5U tRNA modification	Ubiquitous in archaea and eukaryotes, some bacteria	121, 123
QueE	Biosynthesis of preQ0, precursor of tRNA modifications—queuosine and archaeosine	Ubiquitous in all domains of life	99
BioB	Biotin biosynthesis	Widespread in all domains of life	126
ThiC	Thiamine pyrophosphate biosynthesis	Widespread in all domains of life	127
MoaA	Molybdopterin biosynthesis	Widespread in all domains of life	128
PFL-AE	Activating enzyme for pyruvate formate lyase	Widespread in archaea and bacteria	3
RNR-AE	Activating enzyme for anaerobic ribonucleotide reductase	Widespread in archaea and bacteria	3
KAM	Nε-Acetyl-β-lysine biosynthesis for salt tolerance; l-lysine catabolism	Most methanogens and many bacteria	7, 129
EAM	β-Glutamate biosynthesis for salt tolerance	Some methanogens and some bacteria	130
AtsB	Formylglycine generation during sulfatase maturation	Sporadic distribution in all domains of life	3
Dph2	Diphthamide biosynthesis (posttranslational modification of Elp2)	Widespread in archaea and eukaryotes	131

^aQCMT, glutamine C-methyltransferase; PFL-AE, pyruvate formate lyase-activating enzyme; RNR-AE, ribonucleotide reducatse-activating enzyme; KAM, lysine 2,3-aminomutase; EAM, glutamate 2,3-aminomutase.