Sialic acid acetyl groups

Chemical Analysis, Group A polysaccharide is a homo-polymer of D-N-acetyl-mannosamine phosphate which is partially 0-acetylated. Groups B and C are both homopolymers of sialic acid, but group C is 0- acetylated, whereas groiq) B is not. 

Derivatization by permethylation has been shown beneficial for the desorption efficiency and stability of the sialic acid(s) attached [84] however, the permethylation reaction requires strong alkali conditions, which may destroy the alkaline-labile substituents (such as 0-acetyl groups) that may be present as substituents. In order for the selective methylation of sialic acid carboxyl group to achieve a better stability, the same parameters are valid as were presented for glycans (see Section 6.2.5). The coupling of nano-HPLC with MALDI-MS requires a fraction collection step, in order to deposit the separated components arising from the... 

N-Acetylneuraminic acid aldolase (or sialic acid aldolase, NeuA EC 4.1.3.3) catalyzes the reversible addition of pyruvate (2) to N-acetyl-D-mannosamine (ManNAc (1)) in the degradation of the parent sialic acid (3) (Figure 10.4). The NeuA lyases found in both bacteria and animals are type I enzymes that form a Schiff base/enamine intermediate with pyruvate and promote a si-face attack to the aldehyde carbonyl group with formation of a (4S) configured stereocenter. The enzyme is commercially available and it has a broad pH optimum around 7.5 and useful stability in solution at ambient temperature [36]. 

N-Acetylneur-aminic acid Sialic acid (nine C atoms) NeuAc CMP-NeuAc Often the terminal sugar in both N- and 0-linked glycoproteins. Other types of sialic acid are also found, but NeuAc is the major species found in humans. Acetyl groups may also occur as 0-acetyl species as well as N-acetyl. 

Sialic acid occurs naturally as both the N-acetylated and the N-glycoloylated form, the proportion in a given environment being different from one species to another.316 Oxidation of the acetyl group to the glycoloyl group occurs after the formation of 2-acetamido-2-deoxy-D-glucose.317... 

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