Oligosaccharides and Sialic Acid

Glycoproteins and glycolipids are macromolecules that possess covalently linked oligosaccharide side-chains with terminal sialic acid residues at the non-reducing end of the carbohydrate polymer. These glycan structures play important roles in a variety of biological functions. Oligosaccharidoses are caused by defects in enzymes that are involved in the degradation of carbohydrate side-chains on glycoproteins. Sialic acid metabolism disorders can be due to transporter, degradation, and biosynthesis defects of sialic acid. Screening for these disorders occurs by characterization of abnormal storage products (specific oligosaccharides or sialic acid), which are eliminated through urinary excretion from the body. Currently, two screening methods are generally used for detection of these diseases and consist of (1) conventional thin-layer chromatography and (2) (novel) mass spectrometry-based approaches. This chapter describes both screening methodologies, which can easily be adopted by biochemical genetic laboratories for diagnosis of these specific types of inborn errors of metabolism.