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Home >> Dictionary of Bioinformatics, Biochemistry, Biotechnology >> Glucose Alanine Cycle - Gluten Sensitive enteropathy (Coeliac Disease)
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Glucose
C6H12O6 A simple sugar. An immediate source of energy for the cell.
Glucose-alanine cycle
The transport of alanine from the muscle to the liver during starvation. In the liver alanine is converted to pyruvate and eventually to glucose. From the liver, glucose is transported to the muscle where it is converted to pyruvate, which is transaminated to alanine perpetuating cycle.
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Glucose 6-phosphatase
The glycogenolytic enzyme that dephosphorylates glucose-6-phospahets to form glucose which diffuses into the blood. This enzyme is present in the liver but in the muscle.
Glucose
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Glucose fatty acid cycle
In the resting and under conditions of carbohydrate shortage, ketone bodies and free fatty acids are oxidises sparing the oxidation of glucose. The spared glucose inhibits fat mobilization in adipose tissue. This is termed the glucose-fatty acid cycle.
Glucose Invertase; glucose Isomerase
enzymes that catalyse the interconversion of glucose and fructose. Since fructose is chemically more stable that glucose, a mixture of glucose and fructose with the enzyme will mostly yield only fructose. This is useful in the food industry, because fructose is sweeter than glucose and more sweetness per gram can be achieved using fructose. When glucose made by hydrolysis of corn starch is treated with glucose Isomerase, it is converted into a mixture of mostly fructose with a small amount of glucose. Corn starch is hydrolysed by amylases to produce high-fructose corn syrup (HFCS). Invertase acts on sucrose to from glucose and fructose.
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Glucose oxidase
An enzyme from certain molds that catalyses the conversion of glucose into Gluconic acid and hydrogen peroxide (H2O2). The H2O2 formed in the reaction is used to oxidase certain aromatic compounds to from coloured products. The glucose oxidase method is widely used for the estimation of blood and urine glucose.
Glutamate
An acidic amino acid with the side chain –CH2-CH2-COOH. An excitatory neurotransmitter that may become toxic to neurons under certain circumstance. Gluctamate excitotoxicity appears to play a role in nerve cell death in neurodegenerative disorders.
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Glucoside
A glycoside that contains glucose as its carbohydrate moiety.
Glutamate dehydrogenase (GDH)
An enzyme ubiquitous in all mammalian tissues that uses either NAD+ or NADP+ as oxidant to convert glutamate to α-ketoglutarate. Liver GDH is an allosteric enzyme activated by ADP and inhibited by ATP, GTP and NADH. In functions in both amino acid catabolism and biosynthesis.
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Glucose tolerance test
See oral glucose tolerance test.
Glucose 6-phosphatase dehydrogenase (G-6-PD)
An enzyme involved in th pentose phosphate pathway.
Glucose effect
The inhibition of the induction of lac operon glucose.
Glutaminase
An enzyme that removes the amide nitrogen of glutamine.
Glutamine
An amino acid with the side chain ―CH2―CH2 ―CO―NH2. Glutamine is an intermediate in the transfer of amino groups in the biosynthesis and catabolism of a number of amino acids.
Glutamine synthetase
A mitochondrial enzyme present in high concentration in the kidney. It catalyses the conversion of glutamate to glutamine. Formation of glutamine is a major mechanism for the detoxification of NH3 in the brain.
γ-glutamyl cycle
See gama-glutamyl cycle.
γ-glutamyl transpeptidase
See gamma-glutamyl transpeptidase.
Glutaraldehyde
A small reactive molecules containing two aldehyde groups. It is used as a cross-linking fixative.
Glutathione
The tripeptide γ-glutamyl cysteinylglycine that exists in he reduced (GSH) and oxidises (GSSG) forms. GSH is an intracellular reductant and protects the cell against free radicals, peroxides, toxic compounds and the deleterious effects of radiation. It plays an important role in detoxification and maintains protein thiol groups and ascorbic acid in the reduced from. It removes hydrogen peroxide in a reaction catalysed by GPx. It also scavenges superoxide, hydroxyl radical and singlet oxygen non-enzymically. Glutathione plays an important role in the folding of newly synthesised proteins by crosslinking cysteine residues.
Glutathione peroxidase (Gpx)
A tetrameric enzyme with four protein subunits each containing a single selenocysteine residue at the active site. It exists in five isoforms in eukaryotic cells, but the tissue distribution of the isoforms shows high variation. Selenium (se)-dependent and-independent Gpx are the most important and well characterised forms. Both the forms catalyse the reduction of hydroperoxides and hydrogen peroxide at the damage and membrane disorganization by preventing lipid peroxidation. GPx plays an important role in defence against potentially toxic H2O2 and other peroxides including lipid hydroperoxides.
Glutathione redox system
One of he most important intracellular antioxidant defense systems that functions with GSH as the central molecule in association with glutathione reductase, glutathione peroxides and glutathione S-transferase.
Glutathione S-transferases (GSTs)
A superfamily of enzymes that use glutathione phase II enzymes GSTs conjugate reactive electrophiles such as carcinogens, anticancer drugs, metabolic by products and environmental chemical with GSH. GSTs also catalyse reduction of organic hydroperoxides thereby protecting tissues from oxidative stress. GSTs are divided into three distinct superfamily members-cytosolic, mitochondrial, and microsomal. GSTs are highly polymorphic and can be divided into eight classes: alpha, sigma, mu, omega, pi, theta, zeta and MAPEG (Membrane-associated proteins in eicosanoid and glutathione metabolism family).
Glutathione-insulin transhydrogenase
A hepatic enzyme that reduced the disulphide in insulin.
Gluten
A mixture of two proteins, gliadin and glutenin found in the endosperm of wheat grain. The amino acid composition of the two proteins varies, but glutamate (33%) and proline (12%) are the predominant amino acids. The strength of the flour and its suitability for biscuit or bread making depends on the composition of wheat glutens. In coeliac disease, the lining of the intestine shows sensitivity to gluten. This condition is treated by a gluten-free diet.
Gluten-sensitive enteropathy (coeliac disease)
A disease caused by sensitivity to the protein α-gliadin found in wheat. The disease is characterised by villous atrophy and reduction in th absorptive area of the intestine. The clinical symptoms are observable at one year of age with failure to thrive and diarrhoea. Antibodies to α-gliadin may be present in plasma. The conditions is reversible upon withdrawing gluten from the diet.
Glycaemic index (GI)
An index of the blood glucose-increasing potential of the carbohydrate in different foods. It is calculated as the area under the blood glucose curve after a test food is eaten, divided by the corresponding area after a control food (glucose or white bread) is eaten. The value is multiplied by 100 represent a percentage of the control food.
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