Literature Information

Title	Identification and functional expression of genes encoding flavonoid O‐ and C‐glycosidases in intestinal bacteria
Author	Annett Braune, Wolfram Engst, Michael Blaut
DOI	10.1111/1462-2920.12864
Abstract	Gut bacteria play a crucial role in the metabolism of dietary flavonoids and thereby influence the bioactivity of these compounds in the host. The intestinal Lachnospiraceae strain CG19‐1 and Eubacterium cellulosolvens are able to deglycosylate C‐ and O‐coupled flavonoid glucosides. Growth of strain CG19‐1 in the presence of the isoflavone C‐glucoside puerarin (daidzein 8‐C‐glucoside) led to the induction of two proteins (DfgC, DfgD). Heterologous expression of the encoding genes (dfgC, dfgD) in Escherichia coli revealed no C‐deglycosylating activity in the resulting cell extracts but cleavage of flavonoid O‐glucosides such as daidzin (daidzein 7‐O‐glucoside). The recombinant DfgC and DfgD proteins were purified and characterized with respect to their quaternary structure, substrate and cofactor specificity. The products of the corresponding genes (dfgC, dfgD) from E. cellulosolvens also catalysed the O‐deglycosylation of daidzin following their expression in E. coli. In combination with three recombinant proteins encoded by adjacent genes in E. cellulosolvens (dfgA, dfgB, dfgE), DfgC and DfgD from E. cellulosolvens catalysed the deglycosylation of the flavone C‐glucosides homoorientin (luteolin 6‐C‐glucoside) and isovitexin (apigenin 6‐C‐glucoside). Even intact cells of E. coli expressing the five E. cellulosolvens genes cleaved these flavone C‐glucosides and, also, flavonoid O‐glucosides to the corresponding aglycones.

Experimental results

• Enzyme

Uniprot ID: I5AX46

Protein: Putative dehydrogenase

Organism: [Eubacterium] cellulosolvens 6

Length: 357 AA

Taxonomic identifier: 633697 [NCBI]

• Pfam

Source	Domain	Start	End	E-value (Domain)	Coverage
Pfam-A	GFO_IDH_MocA	5	119	3.8e-26	0.975

Program: hmmscan

Version: 3.1b2 (February 2015)

Method: hmmscan --domtblout hmmscan.tbl --noali -E 1e-5 pfam query.fa

Date: Mon Jul 20 14:32:16 2020

Description:

GFO_IDH_MocA

Pfam

This family of enzymes utilise NADP or NAD. This family is called the GFO/IDH/MOCA family in swiss-prot.

InterPro

This group of enzymes utilise NADP or NAD, and is known as the GFO/IDH/MOCA family in UniProtKB/Swiss-Prot. GFO is a glucose–fructose oxidoreductase, which converts D-glucose and D-fructose into D-gluconolactone and D-glucitol in the sorbitol-gluconate pathway. MOCA is a rhizopine catabolism protein which may catalyse the NADH-dependent dehydrogenase reaction involved in rhizopine catabolism. Other proteins belonging to this family include Gal80, a negative regulator for the expression of lactose and galactose metabolic genes; and several hypothetical proteins from yeast, Escherichia coli and Bacillus subtilis.

The oxidoreductase, N-terminal domain is almost always associated with the oxidoreductase, C-terminal domain (see IPR004104).

Information is taken from Pfam and InterPro web site.

• Reaction

Catalyse reaction with expression of I5AX46/I5AX47/I5AX48/I5AX49/I5AX50 simultaneously

daidzin ⇒ daidzein + glucose

References