Glycoproteins moieties

An enzyme may be a protein or a glycoprotein, and consists of at least one polypeptide moiety. The regions of the enzyme that are directly involved in the catalytic process are called the active sites. An enzyme may have one or more groups that are essential for catalytic activity associated with the active sites through either covalent or noncovalent bonds the protein or glycoprotein moiety in such an enzyme is called the apoenzyme, while the nonprotein moiety is called the prosthetic group. The combination of the apoenzyme with the prosthetic group yields the holoenzyme. 

A two-step purification procedure was used for the isolation of lethal protein toxin, Toxin-PC, including 50% ammonium sulphate precipitation followed by DEAE-ion exchange chromatography. Toxin-PC was homogenous in polyacrylamide gel electrophoresis with a SDS-molecular weight of near 15 kDa and devoid of glycoprotein moiety. As described in the results section, lethal Toxin-PC was highly active on isolated heart and nerve... 

Long-chain polyisoprenoid. molecules with a terminal alcohol moiety are called, polyprenols. The dolichols, one class of polyprenols (Figure 8.18), consist of 16 to 22 isoprene units and, in the form of dolichyl phosphates, function to carry carbohydrate units in the biosynthesis of glycoproteins in animals. Polyprenyl groups serve to anchor certain proteins to biological membranes (discussed in Chapter 9). 

Many proteins found in nature are glycoproteins because they contain covalently linked oligo- and polysaccharide groups. The list of known glycoproteins includes structural proteins, enzymes, membrane receptors, transport proteins, and immunoglobulins, among others. In most cases, the precise function of the bound carbohydrate moiety is not understood. 

The resolution of these columns for protein mixtures, however, was comparably poor. The peak capacity for human serum albumin was near 3 during 20 min gradient elution. Improvement has been reached by covalent binding of PEI (M = 400-600) onto a 330 A silica of 5 pm particle size [38], The peak capacities of ovalbumin and 2a -arid glycoprotein were 30-40 (tgradienl = 20 min). Enhanced peak capacity and resolution probably were due to the more diffuse structure of PEI coupled to silane moieties than that of strictly adsorbed on silica and cross-linked (see Sect, 2.2). Other applications of covalently adsorbed PEI are discussed in Sect. 4.1. 

The Use of Selected-Ion Monitoring to Examine the Number of Terminal Galactose Moieties on a Glycoprotein 143... 

Maras, M., Saelens, X., Laroy, W. et al. (1997) In vitro conversion of the carbohydrate moiety of fungal glycoproteins to mammalian-type oligosaccharides - evidence for JV-acetylglucosaminyltransferase-I-accepting glycans from Trichoderma reesei. European Journal of Biochemistry, 249 (3), 701-707. 

Premier, C., Mach, L., Glossl, J. and Marz, L. (1992) The antigenicity of the carbohydrate moiety of an insect glycoprotein, honey-bee (Apis mellifera) venom phospholipase A2. The role of al,3-fucosylation of the asparagine-bound IV-acetylglucosamine. Bio chemicalJournal 284, 377-380. 

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