AbstractDiglycosidases hydrolyze the heterosidic linkage of diglycoconjugates, releasing the disaccharide and the aglycone. Usually, these enzymes do not hydrolyze or present only low activities towards monoglycosylated compounds. The flavonoid degrading fungus Acremonium sp. DSM 24697 produced two diglycosidases, which were termed 6-O-α-rhamnosyl-β-glucosidase I and II (αRβG I and II) because of their function of releasing the disaccharide rutinose (6-O-α-L-rhamnosyl-β-D-glucose) from the diglycoconjugates hesperidin or rutin. In this work, the genome of Acremonium sp. DSM 24697 was sequenced and assembled with a size of ~ 27 Mb. The genes encoding αRβG I and II were expressed in Pichia pastoris KM71 and the protein products were purified with apparent molecular masses of 42 and 82 kDa, respectively. A phylogenetic analysis showed that αRβG I grouped in glycoside hydrolase family 5, subfamily 23 (GH5), together with other fungal diglycosidases whose substrate specificities had been reported to be different from αRβG I. On the other hand, αRβG II grouped in glycoside hydrolase family 3 (GH3) and thus is the first GH3 member that hydrolyzes the heterosidic linkage of rutinosylated compounds. The substrate scopes of the enzymes were different: αRβG I showed exclusive specificity toward 7-O-β-rutinosyl flavonoids, whereas αRβG II hydrolyzed both 7-O-β-rutinosyl- and 3-O-β-rutinosyl- flavonoids. None of the enzymes displayed activity toward 7-O-β-neohesperidosyl- flavonoids. The recombinant enzymes also exhibited transglycosylation activities, transferring rutinose from hesperidin or rutin onto various alcoholic acceptors. The different substrate scopes of αRβG I and II may be part of an optimized strategy of the original microorganism to utilize different carbon sources.
- MeSH
- Acremonium enzymologie genetika MeSH
- flavonoidy metabolismus MeSH
- fungální proteiny genetika metabolismus MeSH
- fylogeneze MeSH
- glykosidhydrolasy genetika metabolismus MeSH
- molekulová hmotnost MeSH
- Pichia genetika MeSH
- rekombinantní proteiny metabolismus MeSH
- sekvenční analýza DNA MeSH
- substrátová specifita MeSH
- Publikační typ
- časopisecké články MeSH
The structure of the carbohydrate moiety of a natural phenolic glycoside can have a significant effect on the molecular interactions and physicochemical and pharmacokinetic properties of the entire compound, which may include anti-inflammatory and anticancer activities. The enzyme 6-O-α-rhamnosyl-β-glucosidase (EC 3.2.1.168) has the capacity to transfer the rutinosyl moiety (6-O-α-l-rhamnopyranosyl-β-d-glucopyranose) from 7-O-rutinosylated flavonoids to hydroxylated organic compounds. This transglycosylation reaction was optimized using hydroquinone (HQ) and hesperidin as rutinose acceptor and donor, respectively. Since HQ undergoes oxidation in a neutral to alkaline aqueous environment, the transglycosylation process was carried out at pH values ≤6.0. The structure of 4-hydroxyphenyl-β-rutinoside was confirmed by NMR, that is, a single glycosylated product with a free hydroxyl group was formed. The highest yield of 4-hydroxyphenyl-β-rutinoside (38%, regarding hesperidin) was achieved in a 2-h process at pH 5.0 and 30 °C, with 36 mM OH-acceptor and 5% (v/v) cosolvent. Under the same conditions, the enzyme synthesized glycoconjugates of various phenolic compounds (phloroglucinol, resorcinol, pyrogallol, catechol), with yields between 12% and 28% and an apparent direct linear relationship between the yield and the pKa value of the aglycon. This work is a contribution to the development of convenient and sustainable processes for the glycosylation of small phenolic compounds.
Bacteria represent an underexplored source of diglycosidases. Twenty-five bacterial strains from the genera Actinoplanes, Bacillus, Corynebacterium, Microbacterium, and Streptomyces were selected for their ability to grow in diglycosylated flavonoids-based media. The strains Actinoplanes missouriensis and Actinoplanes liguriae exhibited hesperidin deglycosylation activity (6-O-α-L-rhamnosyl-β-D-glucosidase activity, EC 3.2.1.168), which was 3 to 4 orders of magnitude higher than the corresponding monoglycosidase activities. The diglycosidase production was confirmed in A. missouriensis by zymographic assays and NMR analysis of the released disaccharide, rutinose. The gene encoding the 6-O-α-L-rhamnosyl-β-D-glucosidase was identified in the genome sequence of A. missouriensis 431(T) (GenBank accession number BAL86042.1) and functionally expressed in Escherichia coli. The recombinant protein hydrolyzed hesperidin and hesperidin methylchalcone, but not rutin, which indicates its specificity for 7-O-rutinosylated flavonoids. The protein was classified into the glycoside hydrolase family 55 (GH55) in contrast to the known eukaryotic diglycosidases, which belong to GH1 and GH5. These findings demonstrate that organisms other than plants and filamentous fungi can contribute to an expansion of the diglycosidase toolbox.
- MeSH
- bakteriální proteiny genetika metabolismus MeSH
- beta-glukosidasa genetika metabolismus MeSH
- chalkonoidy chemie metabolismus MeSH
- disacharidy chemie metabolismus MeSH
- Escherichia coli genetika metabolismus MeSH
- exprese genu MeSH
- flavonoidy chemie metabolismus MeSH
- fylogeneze MeSH
- glykosidy chemie metabolismus MeSH
- hesperidin analogy a deriváty chemie metabolismus MeSH
- hydrolýza MeSH
- klonování DNA MeSH
- Micromonosporaceae klasifikace genetika metabolismus MeSH
- rekombinantní proteiny genetika metabolismus MeSH
- rhamnosa chemie metabolismus MeSH
- substrátová specifita MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
