pancreas, but in lower levels in the brain, kidneys, and lungs. Biosynthesis Vitamin K1 is synthesized from chorismate, a compound produced from shikimate via the shikimate pathway. The conversion of chorismate to vitamin K1 comprises a series of nine steps: Chorismate is isomerized to isochorismate by isochorismate synthase, or MenF (menaquinone enzyme). Addition of 2-oxoglutarate to isochorismate by PHYLLO, a multifunctional protein comprising three different enzymatic activities (MenD, H, and C). Elimination of pyruvate by PHYLLO. Aromatization to yield o-succinyl benzoate by PHYLLO. O-succinylbenzoate activation to corresponding CoA ester by MenE. Naphthoate ring formation by naphthoate synthase (MenB/NS). Thiolytic release of CoA by a thioesterase (MenH). Attachment of phytol chain to the naphthoate ring (MenA/ABC4). Methylation of the precursor at position 3 (MenG). Vitamin K1 is required for plant photosynthesis, where it participates in the Photosystem I electron transport chain. As a result, it is rich in leaves. See also Menatetrenone Vitamin K Vitamin K2 References External links 1,4-Naphthoquinones Vitamers Vitamin K World Health Organization essential medicines Wikipedia medicine articles ready to translate Diterpenes