Phylloquinol biosynthesis is a pathway that occurs in the cytoplast by which geranylgeranyl diphosphate and 2-carboxy-1,4-naphthoquinol becomes phylloquinol, a naphtoquinone designated as vitamin K1 (along with phylloquinone) which posttranslatonally modifies precursors for blood coagualation. The three reactions of the subpathway to synthesize phytyl diphosphate from geranylgeranyl diphosphate are catalyzed by the same enzyme, geranylgeranyl dehydrogenase. This enzyme converts geranylgeranyl diphosphate into dihydrogeranylgeranyl diphosphate, dihydrogeranylgeranyl diphosphate into tetrahydrogeranylgeranyl diphosphate, and tetrahydrogeranylgeranyl diphosphate into phytyl diphosphate. The single reaction of the subpathway to synthesize 2-carboxy-1,4-naphthoquinone from 2-carboxy-1,4-naphthoquinol is catalyzed by 2-carboxy-1,4-naphthoquinol reductase. Next, the chloroplast-membrane-associated enzyme 2-carboxy-1,4-naphthoquinone phytyltransferase (coloured dark green in the image) converts phytyl diphosphate and 2-carboxy-1,4-naphthoquinone into demethylphylloquinone. Then, demethylphylloquinone dehydrogenase uses FAD as a cofactor to convert demethylphylloquinone into demethylphylloquinol. Lastly, demethylphylloquinol methyltransferase converts demethylphylloquinol into phylloquinol.

Phylloquinol Biosynthesis References