Glycosylated Protein Values

Comparative values for glycosylated hemoglobin in man and several experimental (mammalian) species are detailed in Table 4. Examination of the 

Mean standard deviation standard error of mean and range. 

coefficient of variation inter, interassay, between runs intra, intraassay, replicates on single or more specimens. 

Proteins Number of subjects Method Glycosylation (%) CV (%) References 

Serum proteins 12 Fructosamine 1.75 (mean) mmol fructosamine/liter J4 

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Assay procedures for glycosylated proteins incorporate varied methodologies (Al) and have been tailored to accommodate certain specific requirements. The identification and quantitation of the ketoamine link in a variety of proteins have rested mainly on the spectrophotometric thiobar-bituric acid assay. The standpoint is emphasized that short laboratory time assays for ketoamine-adducted proteins hold preeminence over rapid reporting of Hb Aj values as representing glycohemoglobin, unless strict attention to the control of sources of variation is adhered to. Exclusion of free glucose and the labile aldimine adduct is mandatory in all glycosylprotein assays. 

It is desirable to perfect eukaryotic transfection for a number of reasons. Some proteins with therapeutic value have sugar residues attached to them. Such proteins are known as glycosylated proteins. As is the case for insuhn production, it would be beneficial to use cell culture-based processes to produce specific glycosylated proteins with therapeutic potential. However, glycosylated proteins are not... 

While electrospray is used for molecules of all molecular masses, it has had an especially marked impact on the measurement of accurate molecular mass for proteins. Traditionally, direct measurement of molecular mass on proteins has been difficult, with the obtained values accurate to only tens or even hundreds of Daltons. The advent of electrospray means that molecular masses of 20,000 Da and more can be measured with unprecedented accuracy (Figure 40.6). This level of accuracy means that it is also possible to identify post-translational modifications of proteins (e.g., glycosylation, acetylation, methylation, hydroxylation, etc.) and to detect mass changes associated with substitution or deletion of a single amino acid. 

Glycosydation AChE and BChE carry 3 and 9, respectively, N-glycosylation consensus sequences attaching carbohydrate residues to the core protein via asparagines. Different molecular forms of the enzymes in various tissues, show different number and composition of carbohydrate residues. N-glycosylation at all sites was shown to be important for effective biosynthesis, secretion and clearance of ChEs from the circulation. Altered patterns of AChE glycosylation have been observed in the brain and cerebrospinal fluid of Alzheimer s disease (AD) patients, with potential diagnostic value. 

Upper panel The hydropathy profile of the entire 69 kD precursor protein is shown. The abscissa is amino acid residues and the ordinate, positive values indicate hydrophilic. The black and hatched rectangles at the bottom of the figure denote the calculated signal sequence and amino-terminal propeptide domains, respectively. The mature and carboxyl-terminal domains are labeled. N-linked core glycosylation consensus sites are depicted by branched structures. 

This technique is also utilized in the biopharmaceutical industry to determine product homogeneity. Homogeneity is best indicated by the appearance in the gel of a single protein band, exhibiting the predicted pi value. Interpretation of the meaning of multiple bands, however, is less straightforward, particularly if the protein is glycosylated (the bands can also be stained for... 

No alteration of protein half-life has been detected with glycosylated albumin (39) and ferritin (51). However, Jones and Peterson (45) found that fibrinogen survival, which was reduced in diabetic patients with elevated glycemia, could be increased to normal value shortly after insulin therapy. This suggests that a labile Schiff base could play a role in the regulation of fibrinogen turnover. 

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