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.
Differential expression of a putative riboflavin-aldehyde-forming enzyme (raf) gene during development and post-harvest storage and in different tissue of the sporophore in Agaricus bisporus
Cloning and characterisation of a putative riboflavin-aldehyde-forming enzyme gene (raf) from the cultivated mushroom Agaricus bisporus and its expression during morphogenesis are described. Three cDNA clones were isolated following differential screening of cDNA libraries from rapidly expanding sporophores and post-harvest stored sporophores. The cDNA sequence and predicted translation analysis revealed an open reading frame (ORF) of 348 nucleotides encoding a polypeptide of 115 amino acids, with three introns (56–66 bases) interrupting the genomic ORF. Blast X searches of the databases with the gene sequence showed homology (40% identity and 56% similarity) to the riboflavin-aldehyde-forming enzyme gene from Schizophyllum commune. In A.bisporus, the raf gene sequence upstream of the ORF contained a large CT-rich putative regulatory element (−64 to −24 bases) found in highly expressed genes in various mushrooms, and a 6-base motif present in the 3′ end of the genomic sequence, but not in the corresponding 3′ non-coding part of the cDNA, was identified. The raf gene transcripts increased abundantly in rapidly developing sporophores as well in post-harvest stored sporophores. Differential expression of the raf gene transcripts in different tissues of the sporophore was also observed, with higher levels in the stipe compared with the cap and gills. The temporal and spatial expression patterns observed suggest transcriptional regulation of the raf gene during A. bisporus morphogenesis.
Novel method for the determination of the methoxyl content in lignin by headspace gas chromatography.
The paper reports on a headspace gas chromatographic (HS-GC) method for the determination of methoxyl in lignin. The method involves the quantitive cleavage of methoxyl with hydroiodic acid (HI) to form methyl iodide in a closed headspace sample vial at 130 °C for 30 min. After HI has been added, the sample is neutralized by injecting a sodium hydroxide solution; the methyl iodide in the vial was determined by HS-GC using a flame ionization detector. The results showed that the method has an excellent measurement precision (RSD < 0.69%) and accuracy (RSD < 3.5%) for the quantification of methoxyl content in lignin. The present method is simple and accurate and can be used for the efficient determination of methoxy1 content in lignin and related materials.