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By: Richard D. Cummings The definition of a rare sugar is a monosaccharide that is found in small quantities relative to more common sugars in nature, e.g., glucose and N-acetylglucosamine (1-3). There are dozens of rare sugars that are recently gaining attention in regard to nutrition, metabolism...

By: Richard D. Cummings L-Ascorbic acid, vitamin C, is termed a ‘sugar acid’ or ‘acidic sugar’, and is a derivative of glucose with a carboxyl group at C1 (1). In mammals, UDP-glucuronic acid is the source of D-glucuronic acid, the precursor to vitamin C (2). Vitamin C is sometimes referred to as a...

By: Richard D. Cummings Many different monosaccharides from trioses (3-carbon) to decoses (10-carbon) and above are found in nature (1). The most famous nonose (9-carbon) in human glycans is N-acetylneuraminic acid (Neu5Ac) also termed sialic acid. The name sialic acid derives from its discovery in...

By: Richard D. Cummings Sialic acid is a nonose (9-carbon) monosaccharide found in many organisms. All vertebrates have sialic acid, while most invertebrates do not have sialic acid, but there are notable ones that do, as discussed below. In addition, sialic acid is not generated nor found in...

By: Richard D. Cummings One of the most complex polysaccharides in nature is pectin, found in plant cell walls (1,2). Pectin is a family of galacturonic acid-rich polysaccharides that includes homogalacturonan (HG), rhamnogalacturonan I (RG-I), and the substituted galacturonans rhamnogalacturonan II...

By: Richard D. Cummings While plant cellulose is very famous, many commercial products containing cellulose actually use bacterial cellulose. It is often a part of bacterial biofilms, typically of Gram negative (1). This form of cellulose can be highly purified compared to preparations of plant...

By: Richard D. Cummings One of the most unusual glycoproteins and one used commonly in biological research and immunology is KLH, which is derived from the giant keyhole limpet ( Megathura crenulata). The keyhole limpet is a giant aquatic snail (gastropod) with a cone-shaped shell (shell length can...

By: Richard D. Cummings Cholesterol can be glycosylated, and indeed glucosylated cholesterol is common (1). In animal cells, it is a β-D-glucopyranoside derivative of cholesterol (GlcChol), which is generated through a ‘transglycosylation’ pathway in the lysosomes, by the enzymes glucocerebrosidase...

By: Richard D. Cummings The disaccharide lactose, Galβ1-4Glc, is found only in the milk of mammals, and so far, it and extended milk oligosaccharides derived from it, are found nowhere else in nature (1-4). All mammals make milk, of course, but the assortment of oligosaccharides beyond lactose is...

By: Richard D. Cummings O-GlcNAc is a major reversible modification of Ser/Thr residues found on thousands of intracellular glycoproteins in the nucleus, cytoplasm, and mitochondria, and links metabolism via GlcNAc, amino acids, and other intermediates to protein functions (1). The modification has...