A phytoene desaturase homolog gene from the methanogenic archaeon Methanosarcina acetivorans is responsible for hydroxyarchaeol biosynthesis

• A gene from Methanosarcina acetivorans was shown responsible for hydroxyarchaeol biosynthesis.
• The gene encodes a protein with a homology to phytoene desaturase.
• The putative ortholog of the gene tends to be found in hydoxyarchaeol-producers.

Hydroxyarchaeols are the typical core structures of archaeal membrane lipids uniquely produced by a limited number of methanogenic lineages, which are mainly classified in orders Methanosarcinales and Methanococcales. However, the biosynthetic machinery that is used for the biosynthesis of hydroxyarcheol core lipids has not been discovered. In this study, the ma0127 gene from Methanosarcina acetivorans, which encodes a phytoene desaturase-like protein, was found to be responsible for the hydration of a geranylgeranyl group in an archaeal-lipid precursor, sn-2,3-O-digeranylgeranylglyceryl phosphoglycerol, produced in Escherichia coli cells expressing several archaeal enzymes. LC-ESI-tandem-MS analyses proved that hydration occurs at the 2′,3′-double bond of the geranylgeranyl group, yielding a 3′-hydroxylated lipid precursor. This result suggests that the encoded protein MA0127 is a hydratase involved in hydroxyarchaeol biosynthesis, because M. acetivorans is known to produce hydroxyarchaeol core lipids with a 3′-hydroxyphytanyl group. Furthermore, the distribution of the putative orthologs of ma0127 among methanogens is generally in good agreement with that of hydroxyarchaeol producers, including anaerobic methanotrophs (ANMEs).