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By: Richard D. Cummings Glycosphingolipids (GSLs) are sphingolipids, such as ceramide, to which sugars are linked. They are found in virtually all organisms including bacteria, fungi, plants, and animals (1), and many different human and animal parasites (2). Sphingolipids were originally discovered...

By: Richard D. Cummings I am not aware of studies that have directly and quantitatively determined the number of glycoprotein molecules in a cell or the actual number of N-glycan molecules expressed within the glycoproteins in a cell. N-glycans are those linked to asparagine (Asn) residues in the...

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 In the mid 1980s it was strongly believed that all glycosylated proteins arose within the secretory pathway, which generated both secreted and membrane-bound (plasma membrane) glycoproteins. This accepted process was taken to indicate that no glycosylated proteins occurred in...

By: Richard D. Cummings Among the 900-1,400 genes on the human X chromosome (1, 2) [1], there are many genes important in the metabolism of glycomolecules, including glycosyltransferases, glycohydrolases, transporters, and chaperones. Mutations in several of these X-linked genes, either heritable or...

By: Richard D. Cummings In plants, glucose is produced from carbon dioxide (CO 2) and water through photosynthesis, which generates oxygen (O 2) as a byproduct. Without sunlight/photosynthesis, the Calvin Cycle, along with probably the most important enzyme in the world - RuBisCo (Ribulose-1,5...

By: Richard D. Cummings While the N-glycosylation sequon N-X-S/T in glycoproteins of plants, fungi, and animals, is well known, there are many reports of alternative sequons for N-glycosylation in animals (1), including the sequences -N-X-C- (2-4), -N-X-V- (5,6), -N-V-E- (7), -N-X-A- (8), -N-X-G- (9...

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...