- Flavoprotein
Flavoproteins are
proteins that contain anucleic acid derivative ofriboflavin : theflavin adenine dinucleotide (FAD) orflavin mononucleotide (FMN).Flavoproteins are involved in a wide array of biological processes, including, but by no means limited to,
bioluminescence , removal of radicals contributing to oxidative stress,photosynthesis ,DNA repair , andapoptosis . The spectroscopic properties of theflavin cofactor make it a natural reporter for changes occurring within theactive site ; this makes flavoproteins one of the most-studied enzyme families.Discovery
The first mention of a flavoprotein in the scientific literature dates back to 1879, when the work on the composition of cow’s milk resulted in the isolation of a bright-yellow
pigment , that we now know asflavin , but termed lactochrome at the time. By the early 1930s, this samepigment had been isolated from a range of sources, and recognised as a component of thevitamin B complex . Its structure was determined almost simultaneously by two groups in 1934, and given the nameriboflavin , derived from the ribityl side chain and yellow colour of the conjugated ring system.Massey, V. (2000) The chemical and biological versatility of riboflavin, Biochem. Soc. Trans. 28, 283-296.]The first evidence for the requirement of
flavin as anenzyme cofactor came in 1935. Hugo Theorell and coworkers showed that a bright-yellow-colouredyeast protein , identified previously as essential forcellular respiration , could be separated intoapoprotein and a bright-yellow pigment. Neitherapoprotein norpigment alone could catalyse theoxidation ofNADH , but mixing of the two restored theenzyme activity. However, replacing the isolatedpigment withriboflavin did not restoreenzyme activity, despite their being indistinguishable under spectroscopy. This led to the discovery that theprotein studied required notriboflavin butflavin mononucleotide to be catalytically active ] [Theorell, H. (1935) Preparation in pure state of the effect group of yellow enzymes, Biochemische Zeitschrift 275, 344-346.]Similar experiments with
D-amino acid oxidase [Warburg, O., and Christian, W. (1938) Isolation of the prosthetic group of the amino acid oxydase, Biochemische Zeitschrift 298, 150-168.] led to the identification offlavin adenine dinucleotide (FAD) as a second form offlavin utilised byenzymes . [Christie, S. M. H., Kenner, G. W., and Todd, A. R. (1954) NUCLEOTIDES .25. A SYNTHESIS OF FLAVIN ADENINE DINUCLEOTIDE, Journal of the Chemical Society, 46-52.]ee also
Phototropin Cryptochrome References
External links
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* The menu "science" of the program [http://3d-alignment.eu/ STRAP] provides A comprehensive collection of all flavo-proteins with known 3D-structure. It compares the protein structures to elucidate phylogenetic relationships.
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