A modified uronic acid carbazole reaction

A modified colorimetric method for the estimation of n-acetylamino sugars

https://science.sciencemag.org/content/sci/177/4053/949.full.pdf

Lectins: cell-agglutinating and sugar-specific proteins.

Glycosyltransferases catalyze glycosidic bond formation using sugar donors containing a nucleoside phosphate or a lipid phosphate leaving group. Only two structural folds, GT-A and GT-B, have been identified for the nucleotide sugar-dependent enzymes, but other folds are now appearing for the soluble domains of lipid phosphosugar-dependent glycosyl transferases. Structural and kinetic studies have provided new insights. Inverting glycosyltransferases utilize a direct displacement S(N)2-like mechanism involving an enzymatic base catalyst. Leaving group departure in GT-A fold enzymes is typically facilitated via a coordinated divalent cation, whereas GT-B fold enzymes instead use positively charged side chains and/or hydroxyls and helix dipoles. The mechanism of retaining glycosyltransferases is less clear. The expected two-step double-displacement mechanism is rendered less likely by the lack of conserved architecture in the region where a catalytic nucleophile would be expected. A mechanism involving a short-lived oxocarbenium ion intermediate now seems the most likely, with the leaving phosphate serving as the base.

Glycosyltransferases: structures, functions, and mechanisms.

Simple and complex carbohydrates (glycans) have long been known to play major metabolic, structural and physical roles in biological systems. Targeted microbial binding to host glycans has also been studied for decades. But such biological roles can only explain some of the remarkable complexity and organismal diversity of glycans in nature. Reviewing the subject about two decades ago, one could find very few clear-cut instances of glycan-recognition-specific biological roles of glycans that were of intrinsic value to the organism expressing them. In striking contrast there is now a profusion of examples, such that this updated review cannot be comprehensive. Instead, a historical overview is presented, broad principles outlined and a few examples cited, representing diverse types of roles, mediated by various glycan classes, in different evolutionary lineages. What remains unchanged is the fact that while all theories regarding biological roles of glycans are supported by compelling evidence, exceptions to each can be found. In retrospect, this is not surprising. Complex and diverse glycans appear to be ubiquitous to all cells in nature, and essential to all life forms. Thus, >3 billion years of evolution consistently generated organisms that use these molecules for many key biological roles, even while sometimes coopting them for minor functions. In this respect, glycans are no different from other major macromolecular building blocks of life (nucleic acids, proteins and lipids), simply more rapidly evolving and complex. It is time for the diverse functional roles of glycans to be fully incorporated into the mainstream of biological sciences.

/pdf/biological-roles-of-glycans-zowb8sw07y.pdf

Biological Roles of Glycans

https://science.sciencemag.org/content/sci/152/3719/172.full.pdf

Blood-group substances.

Summary

Certain aspects of the biochemistry and genetics of the human A, B, H and Lea blood group characters are reviewed and, on the basis of the biochemical and genetical data, possible pathways are outlined for the biosynthesis of the water-soluble mucopolysaccharides which possess blood group specificity.



Resume

Aprhs un aperpu general de certains aspects biochimiques et genetiques des substances humaines A, B, H et Lea, les auteurs esquissent les voies par lesquelles la biosynthese de ces mucopolysaccharides hydrosolubles, dont chacun possede sa specificite propre, pourrait s'effectuer.



Zusammenfassung

Nach einer einleitenden Ubersicht uber die Biochemie und Genetik der menschlichen Blutgruppeneigenschaften A, B, H und Lea werden die Biosynthesemechanismen der blutgruppenspezifischen wasserlaslichen Mucopolysaccharide diskutiert.

Possible genetical pathways for the biosynthesis of blood group mucopolysaccharides.

Neutralization of the Anti- H Agglutinin in Eel Serum by Simple Sugars

Studies in immunochemistry. 11. The action of dilute alkali on the N-acetylhexosamines and the specific blood-group mucoids.

The presence of α-l-fucosyltransferases in human serum of different ABO, secretor and Lewis blood-group phenotypes was investigated with guanosine diphosphate fucose as the sugar donor and low-molecular-weight oligosaccharides, or a macromolecular glycoprotein, as acceptors. In contrast to the α-2-l-fucosyltransferases in human milk, submaxillary glands and stomach mucosa that occur only in ABH secretors, an enzyme that transfers l-fucose to the C-2 position of non-reducing β-galactosyl residues was found in the serum of all normal ABO donors irrespective of their ABH secretor-nonsecretor status. The only sera in which the α-2-l-fucosyltransferase was not demonstrable were three examples of the blood group Bombay Oh phenotype and one example of the Bh phenotype. An a-3-l-fucosyltransferase that conveyed L-fucose to the C-3 position in N-acetyl-d-glucosamine or d-glucose occurred in all the sera examined including those from donors of the Bombay Oh and Bh phenotypes. a-4-l-Fucosyltransferase activity was virtually absent from the sera, irrespective of the Lewis blood group of the donors.

Winifred M. Watkins

Papers

Blood-group substances.

Possible genetical pathways for the biosynthesis of blood group mucopolysaccharides.

Neutralization of the Anti- H Agglutinin in Eel Serum by Simple Sugars

Studies in immunochemistry. 11. The action of dilute alkali on the N-acetylhexosamines and the specific blood-group mucoids.

α-l-FucosyItransferases in Human Serum from Donors of Different ABO, Secretor and Lewis Blood-Group Phenotypes