The MenG enzyme, a predicted methylase, catalyzes the final methylation step of the biosynthetic pathway from 2-phytyl-1,4-naphthoquinone (demethylphylloquinone) to phylloquinone ( Fig. This suggests phylloquinone trafficking between PG and the thylakoid membrane. But it has been demonstrated that about one-third of phylloquinone is present in PG ( Lohmann et al., 2006 Spicher & Kessler, 2015). Phylloquinone mainly acts as an electron carrier in Photosystem I in the thylakoid membrane ( Brettel et al., 1986). Plant phylloquinone biosynthesis is also connected via shared intermediates to the metabolism of salicylate, tocopherols, chlorophylls, and in some species to anthraquinones. Phylogenetic reconstructions also demonstrate that the plant genes involved in the formation of phylloquinone display a high degree of evolutionary chimerism owing to multiple events of horizontal gene transfer and gene losses. There is today, tough, compelling evidence that plants have evolved an unprecedented metabolic architecture to synthesize phylloquinone, including extraordinary events of gene fusion, highly divergent enzymes and a separated compartmentalization in chloroplasts and peroxisomes. It resulted that most of the plant research on phylloquinone focused historically on the study of its function, while very little was done on its metabolism per se. Until recently, the biosynthesis of phylloquinone in plants was considered identical to that of menaquinone (vitamin K 2) in facultative anaerobic bacteria. In humans and other mammals, it is required as a vitamin (vitamin K 1) for blood coagulation and bone metabolism. Phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone) is a conjugated isoprenoid that serves as a cardinal redox cofactor in plants and some cyanobacteria.

Basset, in Advances in Botanical Research, 2011 Abstract

Cardinal chains lvl 74