The turnover rates of the phosphate groups of flavin-adenine dinucleotide and adenosine triphosphate during oxidative phosphorylation

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Abstract
Paper chromatographic procedures for separation of flavin nucleotides from other phosphates are descr. Incorporation of P32 phosphate into flavin mononucleotide and flavin-adenine dinucleotide (FAD) in liver suspensions is negligible under conditions where ATP rapidly becomes radioactive. Hence the phosphate of free flavin nucleotides apparently plays no direct part in oxidative phosphorylation. Evidence is presented which indicates that the contrary findings of Hummel and Lindberg (who reported a rapid incorporation of [P32] phosphate into FAD) can be explained by incomplete separation of FAD from other phosphates by certain techniques. Contamination with other phosphates occurs when FAD is extracted with phenol from aqueous, saturated, ammonium sulfate solns. and phenol-containing solvents are used for the development of paper chromatograms. FAD (10-5 -10-4 [image]) inhibits the O2 uptake of liver suspensions.