title: Does menaquinone participate in brain astrocyte electron transport?
abstract: Quinone compounds act as membrane resident carriers of electrons between components of the electron transport chain in the periplasmic space of prokaryotes and in the mitochondria of eukaryotes. Vitamin K is a quinone compound in the human body in a storage form as menaquinone (MK); distribution includes regulated amounts in mitochondrial membranes. The human brain, which has low amounts of typical vitamin K dependent function (e.g., gamma carboxylase) has relatively high levels of MK, and different regions of brain have different amounts. Coenzyme Q (Q), is a quinone synthesized de novo, and the levels of synthesis decline with age. The levels of MK are dependent on dietary intake and generally increase with age. MK has a characterized role in the transfer of electrons to fumarate in prokaryotes. A newly recognized fumarate cycle has been identified in brain astrocytes. The MK precursor menadione has been shown to donate electrons directly to mitochondrial complex III.
  
  
  OBJECTIVE
  Vitamin K compounds function in the electron transport chain of human brain astrocytes.
authors.affiliation: BioMérieux, 100 Rodolphe Dr., Durham, NC 27712, United States.
authors.forename: Douglas
authors.initials: D
authors.lastname: Lovern
authors.forename: Beth
authors.initials: B
authors.lastname: Marbois
mesh_terms: D001253:Astrocytes / Q000378:metabolism*; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D004579:Electron Transport / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D015394:Molecular Structure; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism; D011809:Quinones / Q000378:metabolism*; D014451:Ubiquinone / Q000378:metabolism; D010837:Vitamin K 1 / Q000737:chemistry / Q000378:metabolism; D024482:Vitamin K 2 / Q000737:chemistry / Q000378:metabolism*; D024483:Vitamin K 3 / Q000737:chemistry / Q000378:metabolism
chemical_list: D011809:Quinones; D024482:Vitamin K 2; D014451:Ubiquinone; D018698:Glutamic Acid; D024483:Vitamin K 3; D010837:Vitamin K 1; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human