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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 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 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...

By: Richard D. Cummings The endoplasmic reticulum (ER) of many types of cells contain members of a family of UDP-glucuronosyltransferases (UGTs). These enzymes utilize uridine diphosphate glucuronic acid (UDP-GlcA) as a donor and add GlcA to a tremendous variety of aglycone hydrophobic compounds...

By: Richard D. Cummings The major urinary glycoprotein is the Tamm-Horsfall protein (THP), also named uromodulin (Umod), and encoded by UMOD (1-4). Its concentration in urine can be as high as 1-2 mg/mL. It was discovered in 1950 by Tamm and Horsfall in their studies on compounds in urine that could...