Carbohydrate molecular basis

In this article the preparation of one class of carbohydrate-enzyme conjugates, prepared by attachment of dextran to enzymes, is described in some detail and the properties of enzymes modified in this way are discussed. The molecular basis of enzyme stabilization by coupling with dextran is also considered. 

Gangiiosides within lipid rafts also can modulate growth factor receptor- [and src kinase- (65)] mediated tyrosine phosphorylation signaling cascades (66). This modulation can be a carbohydrate—carbohydrate-based interaction (67). Although the molecular basis of such flexible sugar sugar binding is not... 

The acetyl CoA formed in fatty acid oxidation enters the citric acid cycle only if fat and carbohydrate degradation are appropriately balanced. The reason is that the entry of acetyl CoA into the citric acid cycle depends on the availability of oxaloacetate for the formation of citrate, but the concentration of oxaloacetate is lowered if carbohydrate is unavailable or improperly utilized. Recall that oxaloacetate is normally formed from pyruvate, the product of glycolysis, by pyruvate carboxylase (Section 16.3.1). This is the molecular basis of the adage that fats burn in the flame of carbohydrates. 

Many of the techniques used to enrich PTMs at the protein level are applicable at the peptide level. A popular method for enrichment of phosphopeptides is to use an immobilized metal affinity column. The molecular basis for the enrichment is the phosphate affinity to transition metal ions, such as copper, nickel, cobalt, iron, aluminum, gallium, and zinc (142). A comprehensive source for phosphopeptide enrichment strategies can be found in a recent review (143). Lectin-based chromatography is used to enrich for glycopep-tides (144). Lectins are proteins that have an affinity for carbohydrates. With multiple available enrichment options, choosing the right one for the experiment is important. For determining which proteins have a certain PTM, protein-level enrichment can be performed. However, if a type of PTM is of... 

Carbohydrates specifically mediate numerous biological processes that include cell adhesion and differentiation, pathogen invasion, tumor cell metastasis, and inflammatory responses and are therefore of great interest for the generation of therapeutics (/-i). Unfortunately, the molecular basis for most of... 

The molecular basis of the a priori druggability hypothesis is derived from the biophysical study of molecular recognition. The binding energy (AG) of a ligand to a molecular target (e.g., protein, RNA, DNA, carbohydrate) is defined in Eq. (1). 

The discipline of biochemistry developed as chemists began to study the molecules of cells, tissues, and body fluids and physicians began to look for the molecular basis of various diseases. Today, the practice of medicine depends on understanding the roles and interactions of the enormous number of different chemicals enabling our bodies to function. The task is less overwhelming if one knows the properties, nomenclature and function of classes of compounds, such as carbohydrates and enzymes. The intent of this section is to review some of this information in a context relevant to medicine. Students enter medical school with different scientific backgrounds and some of the information in this section will, therefore, be familiar to many students. 

E. Garcia-Hernandez, R. A. Zubillaga, A. Rojo-Dominguez, A. Rodriguez-Romero, and A. Hernandez-Arana, New insights into the molecular basis of lectin-carbohydrate interactions A calorimetric and structural study of the association of hevein to oligomers of JV-acetylglu-cosamine. Proteins, 29 (1997) 467 77. 

The last four chapters of the text complete our study of the molecular basis of life. This chapter and the next three build on your knowledge of the biomolecules (carbohydrates, lipids, proteins, and nucleic acids) and examine the processes that support living organisms. Your attention should now be directed toward gaining an understanding of these processes, where they occur in the cell, their purpose, and, in some cases, key summary reactions. 

THE MAJOR CLASSES of organic compounds common to living systems are lipids, proteins, nucleic acids, and carbohydrates. Carbohydrates are very familiar to us—we call many of them sugars. They make up a substantial portion of the food we eat and provide most of the energy that keeps the human engine running. Carbohydrates are structural components of the walls of plant cells and the wood of trees they are also major components of the exoskeletons of insects, crabs, and lobsters. Carbohydrates are found on every cell surface, where they provide the molecular basis for cell-to-cell communication. Genetic information is stored and transferred by way of nucleic acids, specialized derivatives of carbohydrates, which weTl examine in more detail in Chapter 26. 

The simplest carbohydrates, those that cannot be hydrolyzed into simpler carbohydrates, are called monosaccharides. On a molecular basis, carbohydrates that undergo hydrolysis to produce only 2 molecules of monosaccharide are called disaccharides those that yield 3 molecules of monosaccharide are called trisaccharides and so on. (Carbohydrates that hydrolyze to yield 2-10 molecules of monosaccharide are sometimes called oligosaccharides.) Carbohydrates that yield a large number of molecules of monosaccharides (>10) are known as polysaccharides. 

Polysaccharide (Sections 22.lA and 22.13) A carbohydrate that, on a molecular basis, undergoes hydrolytic cleavage to yield many molecules of a monosaccharide. Also called a glycan. 

In order to understand the molecular basis of oligosaccharide-mediated recognition phenomena, we need to have knowledge of the structure and dynamics of the free carbohydrate ligand in addition to the ligand-receptor complex. In this Chapter, I shall review current knowledge on the former. A discussion of ligand-receptor complexes can be foimd elsewhere in this volume. 

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