Carbohydrates in the edible bird's nest are composed of sialic acid, which may include N-acetylneuraminic acid
, galactosamine, glucosamine, or galactose .
TA is present on the surface of erythrocytes, platelets, and glomeruli, but ordinarily it is covered by a layer of N-acetylneuraminic acid
From over 30 acetylated derivatives of neuraminic acid, N-acetylneuraminic acid
(referred to as sialic acid) is the most common in humans.
(2-4) The most frequent Sias are N-acetylneuraminic acid
(Neu5Ac), N-glycolylneuraminic acid (Neu5Gc) and O-acetylated derivatives thereof (most frequently N-acetyl-9-O-acetylneuraminic acid, Neu5,9A[c.sub.2]) and N-acetyl-9-phosphorylneuraminic acid, although the latter is only a short-lived metabolic intermediate.
Virtually all mammals produce two types: N-acetylneuraminic acid
(Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc).
pallida) submerged in control ASW or in ASW containing the chemosensitizing agent, [10.sup.-5] mol [l.sup.-1] N-acetylneuraminic acid
(NANA), pH 7.62.
Sialic acids are derived from neuraminic acid whose main derivative is N-acetylneuraminic acid
, which is generally used as a synonym for sialic acid (Ledeen and Yu 1976).
These data suggest that acidic transferrins (sialotransferrins) are likely to include both [Asn.sup.432] and [Asn.sup.630] bearing the same biantennary carbohydrate structure composed of 2 N-acetylglucosamine (GlcNAc), 3 mannose (Man), 2 GlcNAc, 2 galactose (Gal), and 2 N-acetylneuraminic acid
(NeuNAc; sialic acid; see structure in Table 2).
An example is a concise synthesis of N-acetylneuraminic acid
(12) from N-acetylmannosamine (11) as outlined in Scheme 2.
There are eight essential saccharides: mannose, glucose, galactose, xylose, fucose, N-acetylglucosamine, N-acetylgalactosamine and N-acetylneuraminic acid
. However, only glucose (found in plants and table sugar) and galactose (found in milk products and certain pectins) are commonly found in the foods we eat.
Since many years, it is known that ML I binds to galactose, but current investigations propose a specific-binding site for ML I consisting of N-acetylglucosamin, galactose and terminal N-acetylneuraminic acid
Sensitizing chemoreceptors for N-acetylated sugars (e.g., N-acetylneuraminic acid
, NANA) and for certain amino compounds (e.g., glycine, alanine, and proline) have thus far been identified.