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Lipid Quinones

1968; Elsevier BV; Linguagem: Inglês

10.1016/b978-1-4831-9942-9.50010-3

0065-2849

T. Ramasarma,

Biochemical Acid Research Studies

A group of quinones with long isoprene side chains, conferring upon them their lipid character, have been discovered in a variety of living cells. This chapter discusses the following three types of naturally occurring lipid quinones: (1) methoxy-substituted 1:4-benzoquinone of ubiquinone type, (2) methyl-substituted l:4-benzoquinone of plastoquinone type, and (3) methyl-substituted 1:4-naphthoquinone of vitamin K type. In animals, only ubiquinone occurs naturally. In higher plants, all three types of lipid quinones occur together. In microorganisms, a varying quinone distribution pattern is known. Ubiquinone is found in molds and yeasts. Several bacteria contain either ubiquinone or vitamin K, some contain none, whereas a few contain both. The most significant metabolic function of the lipid quinones is their participation in the electron transport activities owing to the capacity of the quinones to undergo oxidation reduction. In animals, 2-methylnaphthoquinone compounds exhibit vitamin activity in maintaining the normal function of blood clotting.