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Disorders of Glycoprotein Degradation: Oligosaccharide Analysis
BACKGROUND: Oligosaccharides are low molecular weight carbohydrate chains composed of at least three monosaccharide subunits. They may be covalently coupled to a protein moiety, in which case they are termed glycoconjugates or glycoproteins. Glycoproteins are widely distributed macromolecules that have a vast number of functional implications. The degradation of glycoproteins is thought to be predominantly lysosomal. Lysosomes contain a battery of enzymes required for the complete degradation of glycoproteins. Deficiency of a lysosomal enzyme required for glycoprotein catabolism leads to accumulation of undegraded materials and symptoms of a storage disorder. The undegraded oligosaccharides can be found in the urine of such patients. INDICATIONS FOR TESTING*: Generally most patients exhibit signs and symptoms akin to the mucopolysaccharide storage diseases with radiographic signs of dysostosis multiplex. Some symptoms include skeletal dysplasia, progressive ataxia, myoclonic epilepsy, speech impairment, mental retardation, failure to thrive, organomegaly, coarse facial features, hearing and visual loss, corneal clouding, macular cherry-red spots, growth retardation, and cardiomegaly PROCEDURE: A one-dimensional thin-layer chromatographic (TLC) method on silica gel is available for oligosaccharide screening in urine, with development in two different solvent systems. Oligosaccharides are visualized by spraying with orcinol reagent and heating to 100°C. SAMPLE REQUIREMENTS: 10 cc of urine is required for analysis; random or 24 hour urine is acceptable. INTERPRETATION: The patient's sample results are compared to various oligosaccharide standards as well as positive and normal controls. The excretion patterns vary according to disease. Each disease exhibits a distinctive oligosaccharide pattern on TLC.
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