Metabolomics/Metabolites/Carbohydrates/Sucrose and Other Dissacharides

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Introduction
Sucrose also known as table sugar is one of the few natural chemicals consumed in pure form (other examples are H2O and NaCl). Its average annual consumption is 175 pounds per person in the United States. Table sugar is isolated from sugar cane and sugar beets where it is roughly 14-20% of the weight making it easily extracted. The world production of sugar is around 150 million tons per year.

Disaccharide Structure


Sucrose is not a simple monosaccharide, but a disaccharide composed of two units, glucose and fructose. The structure of sucrose can be deduced from its chemical behavior. Acid hydrolysis will split the molecule into glucose and fructose. Sucrose is a nonreducing sugar meaning it does not have an aldehyde group or is capable of forming one through isomerism. Sucrose also does not form osazones or undergo mutarotation. These findings suggest that the component monosaccharide units are linked by an acetal bridge connecting the two anomeric carbons. X-ray structural analysis confirms this hypothesis: Sucrose is a disaccharide in which the α-D-glucopyranose from of glucose is attached to β-D-fructofuranose in this way. Sucrose has a specific rotation of +66.5 and when treated with aqueous acid the rotation will decrease to a value of -20. This same effect can be achieved using the enzyme invertase on sucrose. The phenomenon is known as the inversion of sucrose and is related to the mutarotation of monosaccharides. The inversion of sucrose includes three separate reactions: hydrolysis of itself to α-D-glucopyranose and β-D-fructofuranose, mutarotation of α-D-glucopyranose to the equilibrium mixture with the β form, and mutarotation of β-D-fructofuranose to the more stable β-D-fructopyranose. Because the value for the rotation of fructose is -92 and the rotation value for glucose is +52.7, the net rotation is negative. This gives an "invert sugar" because it becomes inverted relative to the original solution.

Role of Sucrose when Exposed to Atrazine and Oxidative Stress
Soluble sugars act as metabolite signaling molecules that activate specific or hormone-crosstalk transduction pathways, in addition to playing a central role in plant structure and metabolism. Research was conducted on the different roles of exogenous sucrose in Arabidopsis thaliana plantlets when exposed to the herbicide atrazine and oxidative stress. A transcriptomic approach was utilized along with the employment of CATMAs (complete arabidopsis transcriptome microarrays).

Conditions of xenobiotic stress (stresses from natural substances that are foreign to the human body) and sucrose-induced tolerance in the presence of atrazine, of sucrose, and of sucrose plus atrazine were compared. This comparison displayed atrazine's effect on gene expression and, therefore, the physiology of seedlings. There was as well, due to the larger-than-anticipated impact of atrazine on seedling physiology, potential impairment of protein translation and of reactive-oxygen-species (ROS) defense mechanisms. In addition, there were significant modifications of gene expression pertaining to ROS defense, and repair mechanisms, when there was sucrose-induced protection against atrazine injury. These alterations resulted from the combined influences of sucrose and atrazine. This highlights the significance of the interactions between sucrose and xenobiotic signaling, or of sucrose and ROS signaling.

The resulting sucrose interactions produced characteristic differential expression of gene families including ascorbate peroxidases, glutathione-S-transferases and cytochrome P450s. Using these genes as molecular markers is expected to substantially progress future research of xenobiotic tolerance and phytoremediation (the use of certain plants to clean up soil, sediment, and water contaminated with metals and/or organic contaminants).

Comparative observations between the atrazine-induced stress situation and the sucrose-atrazine protection situation via the transcriptomic approach has provided new insight into xenobiotic-signaling pathways, xenobiotic tolerance pathways, and identifying novel xenobiotic tolerance pathways. Research conducted on these reactions, in environments containing high concentrations of atrazine, prior to the transcriptomic approach produced trivial data.

Early TF and gene target studies involving sucrose-induced tolerance are expected to be more useful when investigating sugar-induced tolerances towards other xenobiotics. Sucrose has, as well, been proven to induce a tolerance towards other xenobiotics.

References:

Organic Chemisty 6th Edition by Vollhardt (pg1142-1143)

http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=18053238

www.medterms.com

http://www.envirotools.org/factsheets/phytoremediation.shtml

http://www.catma.org/database/ KEGG:

Web source 1

1.[]

2. The main focus of this source is to provide a definition of disaccharides along with a general description of basic aspects such as composition, structure, formation, and a list of common disaccharides including sucrose, lactose, maltose, trehalose, and cellulobiose, and what monosaccharides they’re composed of, and their linkage types.

3. Reducing disaccharide : monosaccharide components bonded by hydroxyl groups. Non-reducing disaccharide : components bond through their anomeric centers Dehydration reaction : chemical reaction involving loss of water from reacting molecule Glycosidic bond : functional group bonding a carbohydrate molecule to another molecule. The bond between hemiacetal group of the saccharide and hydroxyl group of another organic compound. Diastereoisomers : stereoisomers that are not enantiomers (mirror images) and that have different physical properties and react differently from one another.

4. This source briefly discusses formation of disaccharides which we covered in class using sucrose. It also describes alpha and beta linkages between the components of common disaccharides, some of which we’ve discussed in class.

Web source 2

1.[]

2. This source primarily focuses on the difference between reducing and non-reducing disaccharides. For both types, it lists the names, discusses and shows images of the structures of the disaccharide, and provides some information about the uses or sources of the disaccharide.

3. Cellobiose : 4-O-β-D-glucopyranosyl-D-glucose, results from the hydrolysis of cellulose by bacteria Endocellulase : enzyme that hydrolyzes cellulose Lactose intolerance : A condition in which the enzyme lactase is absent or non-functioning and lactose cannot be broken down into its monosaccharide components Galactosemia : A condition that is an inability to process the resulting D-galactose after hydrolysis. Furanosyl unit : five of these are present in sucrose

3.This source connects to the course material through it’s description of the structures of the components of the disaccharides, discussion of the meaning of reducing and non-reducing sugars, and alpha and beta linkages.

Web source 3

1.[]

2. The purpose of this source is to provide information about the pathway of sucrose synthesis, which occurs in plants. It includes an illustration of the process, and provides information pertaining to the starting products, intermediate, and enzymes required.

3. Photosynthesis : carbohydrates are synthesized from CO2 and water, releasing oxygen, and using light to provide energy. Activated glucose : uridine disphospate (UDP) glucose, which consists of the pyrophosphate group, the pentose sugar ribose, glucose, and uracil. Nucleotide group : phosphorylated pentose sugar that is linked via an N-glycosidic bond to a purine or pyrimidine base. Photophosphorylation : production of ATP using the energy of sunlight for the phosphorylation reaction

4. The purpose of this source is to provide information about sucrose synthesis as a pathway, which we discussed in class as part of the topic of photosynthesis.

Peer-reviewed Articles:

“Fermentation of High Concentrations of Maltose by Saccharomyces cerevisiae Is Limited by the COMPASS Methylation Complex”

1.[]

2. This source is about late stage fermentation of high concentrations of maltose (main carbohydrate in brewer’s wort) in yeast used to produce beer. It discusses the COMPASS methylation complex, which methylates lysine 4 on histone H3, controls maltose utilization genes in late-stage fermentation.

3. Fermentation : oxidation of organic compounds that result in energy production, with sugars as a typical substrate, and ethanol, hydrogen, and lactic acid as typical byproducts. Methylation : replacement of a hydrogen atom with a methyl group. Telomeric region : DNA region at the end of a chromosome that consists of repeated sequences and protects the genetic material from damage. Northern blotting : a method of RNA analyzation using electrophoresis. Western blotting : a method of detecting specific proteins using electrophoresis.

“Adaptation of Sucrose Metabolism in the Escherichia coli Wild-Type Strain EC3132†”

1.[]

2.This article pertains to an experiment involving the cloning, sequencing, and analysis of the csc gene locus from E. coli wild-type strain EC3132 that allows cells to utilize sucrose as a carbon source.

3. Sucrose permease : Fructokinase : Sucrose hydrolase : Phosphoenolpyruvate :

“Metabolic Fluxes in Corynebacterium glutamicum during Lysine Production with Sucrose as Carbon Source”

1.[]

2. Metabolic fluxes were determined for Corynebacterium glutamicum grown on sucrose medium in a study about the process of molasses based industrial production.

3. Metabolic flux : Pentose Phosphate Pathway : Fructose-specific phosphotransferase system (PTS): Isocitrate dehydrogenase : NADPH :

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