Myxoxanthophyll is a carotenoid glycoside in cyanobacteria that is of unknown biological significance. The sugar moiety of myxoxanthophyll in Synechocystis sp. strain PCC 6803 was identified as dimethyl fucose. The open reading frame sll1213 encoding a fucose synthetase orthologue was deleted to probe the role of fucose and to determine the biological significance of myxoxanthophyll in Synechocystis sp. strain PCC 6803. Upon deletion of sll1213, a pleiotropic phenotype was obtained: when propagated at 0.5 μmol photons/m2/s, photomixotrophic growth of cells lacking sll1213 was poor. When grown at 40 μmol photons/m2/s, growth was comparable to that of the wild type, but cells showed a severe reduction in or loss of the glycocalyx (S-layer). As a consequence, cells aggregated in liquid as well as on plates. At both light intensities, new carotenoid glycosides accumulated, but myxoxanthophyll was absent. New carotenoid glycosides may be a consequence of less-specific glycosylation reactions that gained prominence upon the disappearance of the native sugar moiety (fucose) of myxoxanthophy11. In the mutant, the N-storage compound cyanophycin accumulated, and the organization of thylakoid membranes was altered. Altered cell wall structure and thylakoid membrane organization and increased cyanophycin accumulation were also observed for ∆slr0940K, a strain lacking zeta-carotene desaturase and thereby all carotenoids but retaining fucose. Therefore, lack of myxoxanthophyll and not simply of fucose results in most of the phenotypic effects described here. It is concluded that myxoxanthophyll contributes significantly to the vigor of cyanobacteria, as it stabilizes thylakoid membranes and is critical for S-layer formation

cyanobacteria, myxoxanthophyll, Synechocystis, thylakoid membrane

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

CO[C@@H]1[C@H](C)O[C@@H](OC(/C=C/C(C)=C/C=C/C(C)=C/C=C/C(C)=C/C=C/C=C(C)/C=C/C=C(C)/C=C/C2=C(C)CC(O)CC2(C)C)C(C)(C)O)[C@@H](OC)[C@@H]1O

759.081 g/mol (C₄₈H₇₀O₇)

Fucosylated oligosaccharides are interesting molecules due to their bioactive properties. In particular, their application as active ingredient in milk powders is attractive for dairy industries. The objective of this study was to characterize the glycosyl hydrolase family 29 α-fucosidase produced by Aspergillus niger and test its ability to transfucosylate lactose with a view towards potential industrial applications such as the valorization of the lactose side stream produced by dairy industry. In order to reduce costs and toxicity the use of free fucose instead of environmentally questionable fucose derivatives was studied. In contrast to earlier studies, a recombinantly produced A. niger α-fucosidase was utilized. Using pNP-fucose as substrate, the optimal pH for hydrolytic activity was determined to be 3.8. The optimal temperature for a 30-min reaction was 60 °C, and considering temperature stability, the optimal temperature for a 24-h reaction was defined as 45 °C For the same hydrolysis reaction, the kinetic values were calculated to be 0.385 mM for the KM and 2.8 mmol/mg/h for the Vmax. Transfucosylation of lactose occurred at high substrate concentrations when reaction time was elongated to several days. The structure of the product trisaccharide was defined as 1-fucosyllactose, where fucose is α-linked to the anomeric carbon of the β-glucose moiety of lactose. Furthermore, the enzyme was able to hydrolyze its own transfucosylation product and 2'-fucosyllactose but only poorly 3-fucosyllactose. As a conclusion, α-fucosidase from A. niger can transfucosylate lactose using free fucose as substrate producing a novel non-reducing 1-fucosyllactose.

Aspergillus niger, 1-fucosyllactose, fucosyllactose, non-reducing sugar, transfucosylation, α-fucosidase

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
1,4	bDGalp	104.2	72.3	73.8	69.8	76.7	62.3
1	bDGlcp	98.5	73.7	75.5	79.5	76.2	61.2
	aLFucp	96.5	68.6	70.7	73.0	68.5	16.6


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
1,4	bDGalp	4.456	3.545	3.666	3.926	3.727	3.773
1	bDGlcp	4.658	3.423	3.674	3.701	3.598	3.826-3.971
	aLFucp	5.283	3.838	3.913	3.833	4.220	1.216


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
1,4	bDGalp	104.2/4.456	72.3/3.545	73.8/3.666	69.8/3.926	76.7/3.727	62.3/3.773
1	bDGlcp	98.5/4.658	73.7/3.423	75.5/3.674	79.5/3.701	76.2/3.598	61.2/3.826-3.971
	aLFucp	96.5/5.283	68.6/3.838	70.7/3.913	73.0/3.833	68.5/4.220	16.6/1.216

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

C[C@@H]1O[C@@H](O[C@@H]2O[C@H](CO)[C@@H](O[C@@H]3O[C@H](CO)[C@H](O)[C@H](O)[C@H]3O)[C@H](O)[C@H]2O)[C@@H](O)[C@H](O)[C@@H]1O

488.439 g/mol (C₁₈H₃₂O₁₅)