Flavoproteins are proteins that contain a nucleic acid derivative of riboflavin: flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN). Flavoproteins are involved in a wide array of biological processes, such as photosynthesis, DNA repair and natural product biosynthesis. It should be noted that 5%-10% of flavoproteins have a covalently linked flavin prosthetic group. Such covalent linkages benefit the holoenzyme in several ways including improving the stability and catalytic potency. During the past decade, significant progress has been made in covalent flavoproteins, especially with respect to enzyme-dependent biogenesis and discovery of novel linkage types. The present review gives a condensed overview of investigations published from March 2009 to December 2021, with emphasis on the discovery, biogenesis and their catalytic role in natural product biosynthesis.
Flavoproteins/metabolism* ; Flavin-Adenine Dinucleotide/metabolism* ; Flavin Mononucleotide/metabolism* ; Riboflavin ; Biological Products

Riboflavin is a constituent of coenzyme, FMN, FAD and its content varies according to the physiological and nutritional status. However, the measurement of its content is so disputable that a new technique to determine its content has been developed, done by determination of glutathione reductase activity in red blood cell hemolysate. With this technique, the effect of various anesthetic agents (ether, halothane, tetracaine) upon riboflavin metabolism has been studied by the authors. In conclusion, the effects of anesthetics upon riboflavin metabolism are insignificant.
Anesthetics ; Erythrocytes* ; Flavin Mononucleotide ; Flavin-Adenine Dinucleotide ; Glutathione Reductase ; Glutathione* ; Halothane ; Metabolism ; Nutritional Status ; Riboflavin

An activation domain in p67(phox) (residues 199-210) is critical for regulating NADPH oxidase activity in cell-free system [10] To determine the steady state reduction of FAD, thioacetamide-FAD was reconstituted in gp91(phox), and the fluorescence of its oxidised form was monitored. Omission of p67(phox) decreased the steady state reduction of the FAD from 28% to 4%, but omission of p47(phox) had little effect. A series of the truncated forms of p67(phox) were expressed in E.coli to determine the domain in p67(phox) which is essential for regulating the steady state of FAD reduction. The minimal length of p67(phox) for for regulating the steady state of FAD reduction is shown to be 1-210 using a series of truncation mutants which indicates that the region 199-210 is also important for regulating electron flow within flavocytochrome b(558). The deletion of this domain not only decreased the superoxide generation but also decreased the steady state of FAD reduction. Therefore, the activation domain on p67(phox) regulates the reductive half-reaction for FAD, consistent with a dominant effect on hydride/electron transfer from NADPH to FAD.
Amino Acid Sequence ; Base Sequence ; Cell Membrane/metabolism ; Cell-Free System ; DNA Primers ; Flavin-Adenine Dinucleotide/*metabolism ; Humans ; Kinetics ; Membrane Glycoproteins/*metabolism ; Molecular Sequence Data ; NADH Dehydrogenase/metabolism ; *NADPH Oxidase ; Neutrophils/enzymology/metabolism ; Oxidation-Reduction ; Peptide Fragments/chemistry ; Phosphoproteins/*chemistry/*metabolism ; Polymerase Chain Reaction ; Sequence Deletion