Enzymic and Chemical Conversions

IH-NMR spectroscopy is suitable for following the course of reactions either directly in the NMR-tube or by analysis of isolated reaction products. Simultaneous measurements of substrate and product concentrations allows under proper conditions the deduction of kinetic reaction parameters (Friebolin et al 1981c). Alternatively, the formed products can be isolated and analysed separately by NMR spectroscopy. For example in the saponification of sialic acid methyl esters under mild alkaline conditions both types of approaches are useful (Haverkamp et al 1982). The potency of NMR spectroscopy as a real-time analytical probe is in particular evident in the study of enzyme reactions. 

GalNAcp(l-4)Galp(l-4)GalNAcp(l-3)Galp(l-3)[Neu5Gca(2-6)]GalNAc-ol 1.669 2.659 n.d. 

The positional specificity of sialidases can be monitored by the action of the enzymes on mixtures of isomeric sialyllactoses (Friebolin et al. 1981c). In the same study also kinetic parameters of these enzyme reactions were determined. For sialidase isolated from Newcastle disease virus Paulson et al. (1982) demonstrated by 500 MHz H-NMR spectroscopy that this enzyme hydrolyzes preferentially sialic acid residues a(2-3)-linked to aj-acid glycoprotein. 

The specificity of a colostrum sialyltransferase was investigated by Van den Eijnden et al. (1980) using glycopeptides derived from asialo-aj-acid glycoprotein as substrates. The positional specificity as well as the branch specificity of the enzyme were studied. 

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