Biomaterial Database

One- and two-electron reduction of quinones by rat liver subcellular fractions. 1994

M Nakamura, and T Hayashi

Department of Biophysics, Hokkaido University, Sapporo.

NAD(P)H-quinone (menadione, Trolox C quinone, and alpha-tocopherol quinone) reductase activity of rat liver subcellular fractions was observed optically at 340-400 nm, and oxygen radical generation was demonstrated using the ESR spin trap, 5,5'-dimethyl-1-pyrroline-1-oxide. NAD(P)H-menadione reductase activity of the fractions decreased in the order: cytosol > microsomes > plasma membranes. Although more than 65% of the activity of microsomes and plasma membranes was inhibited on the addition of dicoumarol, no change in the menadione-mediated formation of oxygen radicals by either fraction was observed. As judged from the intensity of ESR signals, the menadione-mediated oxygen radical formation by plasma membranes was only one-tenth as great as that by microsomes. No generation of oxygen radicals in the NAD(P)H-menadione reductase reaction by cytosol was found, and the activity was abolished in the presence of dicoumarol, an inhibitor of DT-diaphorase. It is concluded that plasma membranes reduce quinones by way of two-electron transfer and that the activity may prevent cellular quinone toxicity. NAD(P)H-alpha-tocopherol quinone reductase activity was confirmed in all cellular fractions [Hayashi et al. (1992) Biochem. Pharmacol. 44, 489-493] and this activity was also inhibited by dicoumarol, suggesting that it was due to DT-diaphorase.

UI	MeSH Term	Description	Entries
D008099	Liver	A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.	Livers
D008297	Male		Males
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D010100	Oxygen	An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.	Dioxygen,Oxygen-16,Oxygen 16
D004583	Electrons	Stable elementary particles having the smallest known negative charge, present in all elements; also called negatrons. Positively charged electrons are called positrons. The numbers, energies and arrangement of electrons around atomic nuclei determine the chemical identities of elements. Beams of electrons are called CATHODE RAYS.	Fast Electrons,Negatrons,Positrons,Electron,Electron, Fast,Electrons, Fast,Fast Electron,Negatron,Positron
D005609	Free Radicals	Highly reactive molecules with an unsatisfied electron valence pair. Free radicals are produced in both normal and pathological processes. Free radicals include reactive oxygen and nitrogen species (RONS). They are proven or suspected agents of tissue damage in a wide variety of circumstances including radiation, damage from environment chemicals, and aging. Natural and pharmacological prevention of free radical damage is being actively investigated.	Free Radical
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013347	Subcellular Fractions	Components of a cell produced by various separation techniques which, though they disrupt the delicate anatomy of a cell, preserve the structure and physiology of its functioning constituents for biochemical and ultrastructural analysis. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p163)	Fraction, Subcellular,Fractions, Subcellular,Subcellular Fraction
D014810	Vitamin E	A generic descriptor for all TOCOPHEROLS and TOCOTRIENOLS that exhibit ALPHA-TOCOPHEROL activity. By virtue of the phenolic hydrogen on the 2H-1-benzopyran-6-ol nucleus, these compounds exhibit varying degree of antioxidant activity, depending on the site and number of methyl groups and the type of ISOPRENOIDS.
D014812	Vitamin K	A lipid cofactor that is required for normal blood clotting. Several forms of vitamin K have been identified: VITAMIN K 1 (phytomenadione) derived from plants, VITAMIN K 2 (menaquinone) from bacteria, and synthetic naphthoquinone provitamins, VITAMIN K 3 (menadione). Vitamin K 3 provitamins, after being alkylated in vivo, exhibit the antifibrinolytic activity of vitamin K. Green leafy vegetables, liver, cheese, butter, and egg yolk are good sources of vitamin K.