title: Reconstitution of liver NADH: cytochrome b5 oxidoreductase and of Desulfovibvio vulgaris flavodoxin with 1-carba-1-deazaflavin.
abstract: Flavin-free cytochrome b5 reductase was reconstituted with 1-deazaflavin and 5-deazaflavin mononucleotides and dinucleotides. The 5-deazaenzyme functioned in transhydrogenation reactions but lacked electron transferase activity. The 1-deazaenzyme was fully competent for both input and output reactions. The flavin reduction rate was lowered about sevenfold upon N-1 substitution of FAD, but hydrogen abstraction from NADH remained the limiting step. Autoxidation of the reduced enzyme was more rapid than with the normal cofactor. Oxidation was accompanied by appearance of a transient blue-type semiquinone and superoxide ion production. Flavin-free apoflavodoxin was reconstituted with 1-deaza-1-carbaflavin mononucleotide (1-deaza-FMN). Its behaviour toward dithionite and oxygen was qualitatively highly similar to that of native flavodoxin. These observations contrast with the fact that apoflavocytochrome b2 could not be reconstituted with 1-deaza-FMN [Pompon. D. and Lederer, F. (1979) Eur. J. Biochem. 96. 571-579]. These results, as well as other data from the literature, are discussed in the light of existing hypotheses, which try to correlate flavin protein interactions and flavoprotein function.
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D002417:Cattle; D003579:Cytochrome Reductases / Q000378:metabolism*; D042966:Cytochrome-B(5) Reductase; D003901:Desulfovibrio / Q000201:enzymology*; D004227:Dithionite; D005486:Flavin Mononucleotide / Q000494:pharmacology; D005182:Flavin-Adenine Dinucleotide / Q000031:analogs & derivatives* / Q000494:pharmacology; D007700:Kinetics; D008862:Microsomes, Liver / Q000201:enzymology*; D013053:Spectrophotometry
chemical_list: D005182:Flavin-Adenine Dinucleotide; D004227:Dithionite; C023406:1-deaza-FAD; D005486:Flavin Mononucleotide; D003579:Cytochrome Reductases; D042966:Cytochrome-B(5) Reductase