Fungal riboflavin 5'-hydroxymethyl dehydrogenase catalyzes formation of both the aldehyde (riboflavinal) and the acid (riboflavinoic acid).
The purified enzyme from Schizophyllum commune that readily catalyzes the oxidation of the 5'-hydroxymethyl function of riboflavin (vitamin B2) with a redox dye and O2 to form the 5'-aldehyde can more slowly further oxidize the 5'-aldehyde to the 5'-acid. Hence, the formation of these so-called 'schizoflavins' can be accounted for by the action of one enzyme.
[47] Isolation and identification of schizoflavins
Publisher Summary This chapter discusses the schizoflavins. The flavin found in the culture broth of Schizophyllum commune , a basidiomycete, is named “schizoflavin (SF)” and, with the recognition of two such flavins, they are called SF 1 and SF 2 , respectively. It was suggested by an enzymic study that riboflavin is apparently converted via SF2 to SF and that SF 2 is a direct precursor of SF 1 . Schizoflavins are thought to be biochemically interesting compounds in connection with the findings that SF 1 participates in the L-malate accumulation in S. commune and stimulates hydrocarbon fermentation by Candida species. Both SF 1 and SF 2 solutions have yellowish green fluorescence and are reduced by sodium dithionite and reversibly oxidized by air. Moreover, the polarographic behaviors of schizoflavins indicate that both the compounds of SF 1 and SF 2 function as a flavin. The paper chromatographic and electrophoretic behaviors of schizoflavins are discussed in this chapter. On electrophoresis, the SF 1 spot moves toward the anode as flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD), while the SF 2 spot moves slightly toward the cathode just as riboflavin does. The ultraviolet (UV) and visible absorption spectra are measured in water, 0.05 N sodium hydroxide, and 3 N hydrochloric acid, respectively. The absorption peaks of SF 1 or SF 2 are at 223, 267, 374, and 446 nm that agrees very closely with those of riboflavin.
Stretching frequency versus bond distance correlation of OD(H)⋯Y (Y N, O, S, Se, Cl, Br, I) hydrogen bonds in solid hydrates
From a compilation of spectroscopic and structural data of solid hydrates 61 different compounds containing more than 250 OD(H)⋯Y groups have been selected, for which uncoupled OD stretching frequencies, hydrogen bond distances and assignments of sufficient reliability and accuracy are available. ν(OD) versus R(O⋯Y) and R(H⋯Y) diagrams and calculated correlation curves are presented for Y  N, O, S, Se, Cl, Br, I. Depending on the scatter of points and the number of data included in the plots the predictive value and the statistical significance varies from very high for O, S and Cl acceptors down to rather poor for Br and I acceptors. At equal bond distances the frequencies may differ by up to about 150 cm−1 depending on the specific chemical nature of the proton acceptors included in a plot, while the influence of different cation—water contacts is less significant and distinct. Anion effects play, therefore, a dominant role in producing large scatters, while action effects and experimental inaccuracies are of minor importance. Furthermore it is shown, that the relation between ν(OD) and ν(OH) frequencies is almost perfect and the frequency—distance correlations involving ν(OD) are also representative without serious restrictions for corresponding correlations involving ν(OH).