Pneumococcal cell wall polysaccharide (C-PS), a contaminant in pneumococcal capsular polysaccharide (Pn-PS) vaccines is degraded by mild deamination of the 4-amino-2-acetamido-2,4,6-tri-deoxy-galactose (AAT) in C-PS, which was carried out by addition of 5% aqueous sodium nitrite to a solution of polysaccharide in 5% aqueous acetic acid. Glycosidic linkage and functional groups such as O-acetates, phosphodiesters, and pyruvates were preserved under the conditions. The small fragments from degraded C-PS were removed by ultrafiltration or dialysis to provide essentially C-PS free Pn-PS. Because of the presence of AAT in its structure the deamination is not suitable for the purification of type 1 Pn-PS. Meanwhile, the mass and NMR spectroscopic analysis on the deamination products suggests that both type 1 Pn-PS and C-PS degraded following a major pathway of 5,4-hydride shift, cleavage of AAT O5-C1 bond, C1 hemiacetal formation, and its hydrolysis to release neighboring GalA- in type 1 Pn-PS and GalNAc(6-O-PCho)- in C-PS

mechanism, degradation, deamination, cell wall polysaccharide, pneumococcal capsular polysaccharide

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,4	67%Ac
3	aDGalpA	97.2	69.1	68.8	73.7	70.8	179.8
	bDGalpA	97.2	70.8	78.5	67.5	75.1	179.3


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,4	67%Ac
3	aDGalpA	5.28	3.92	4.23	5.69	4.92	-
	bDGalpA	4.65	3.62	3.84	4.52	4.35	-


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,4	67%Ac
3	aDGalpA	97.2/5.28	69.1/3.92	68.8/4.23	73.7/5.69	70.8/4.92	
	bDGalpA	97.2/4.65	70.8/3.62	78.5/3.84	67.5/4.52	75.1/4.35	

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

CC(=O)O[C@H]1[C@@H](C(=O)O)O[C@H](O[C@H]2[C@@H](O)[C@@H](C(=O)O)O[C@@H](O)[C@@H]2O)[C@H](O)[C@H]1O

412.3 g/mol (C₁₄H₂₀O₁₄)