Neuraminic acid degradation

The second pathway for the formation of 3-deoxyulosonic acids is, at present, represented only by the condensation of pyruvate with iV -acetyl-n-mannosamine to form a nonulosaminic acid (iV-acetylneuraminic acid). - This reaction is readily reversible, but the point of equilibrium is 90 per cent toward degradation and 10 per cent toward synthesis of the iV-acetyl-neuraminic acid. ... 

The greatest advances at the enzyme level have been in understanding the inborn errors associated with lipid metabolism (27). At least nine of these diseases have been described at the enzyme level (Table II). The first five diseases listed in Table II involve enzymes which successively degrade Cer-Glc-Gal-(NeuNAc)-GalNAc-Gal to ceramide, glucose, galactose, and neuraminic acid. No genetic diseases associated... 

The enzymic degradation of the gangliosides in normal tissues was also studied. This degradation started with cleavage of the N-acetyl-neuraminic acid residues, and was followed by the cleavage of the other sugars linked to the ceramide moiety.221... 

An increased urinary excretion of free A-acetylneuraminic acid has been detected in patients with Salla disease, which is a newly reported type of lysosomal storage disorder.Patients appear to lack an iV-acetylneuraminyl lyase or some lysosomal enzyme responsible for the degradation of AT-acetyl-neuraminic acid. 

Muramic acid has been determined quantitatively by a procedure that involves its degradation to acetaldehyde via lactic acid. Acetaldehyde was measured spectrophotometrically, and other components present in hydrolysates of bacterial cell walls did not interfere with the determination. The analysis of natural and synthetic N- and O-acylated sialic acids by g.l.c. of the TMS ethers has been described. The 0-acyl groups were not lost when iV-trimethylsilyl-imidazole was used as the silylating reagent. A quantitative determination of neuraminic acid by g.l.c.-m.s. (using multiple ion-detection) has been reported. A modified periodate-resorcinol procedure, which avoids extraction of the... 

The procedure consists of stepwise enzymatic degradation of chemically prepared neuraminic acid derivatives (3) to give the corresponding modified ManNAc analogs (1), which is followed by subsequent neuraminic acid reconstruction in the presence of [3- C] labeled pyruvate (21). To ensure complete conversion in the desired direction the first step was promoted by cofactor-dependent reduction of pyruvate the second, synthetic step, was uncoupled by destruction of the nucleotide cofactor before addition of labeled pyruvate. Sialic acids such as 20 with high label incorporation (> 87%) were obtained in good yields (46-76%). 

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