pentose phosphate pathway


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pathway

 [path´wa]
a course usually followed. In neurology, the nerve structures through which a sensory impression is conducted to the cerebral cortex (afferent pathway), or through which an impulse passes from the brain to the skeletal musculature (efferent pathway). Also used alone to indicate a sequence of reactions that convert one biological material to another (metabolic pathway).
accessory pathway (accessory conduction pathway) extra muscle tissue between the atrium and ventricle that bypasses all or part of the normal conduction system. When the ventricles are activated prematurely via this pathway, initial forces are slow, producing the delta wave of wolff-parkinson-white syndrome, and preexcitation is said to exist; the delta wave causes the PR interval to shorten and the QRS interval to broaden.
alternative complement pathway see complement.
amphibolic pathway a group of metabolic reactions with a dual function, providing small metabolites for further catabolism to end products or for use as precursors in synthetic, anabolic reactions. The tricarboxylic acid cycle is an example. See also anabolism and catabolism.
biosynthetic pathway the sequence of enzymatic steps in the synthesis of a specific end-product in a living organism.
classical complement pathway see complement.
common pathway of coagulation the steps in the mechanism of coagulation (see clotting) from the activation of factor x through the conversion of fibrinogen to fibrin. See also intrinsic pathway of coagulation and extrinsic pathway of coagulation.
concealed accessory pathway an accessory pathway that has only retrograde conduction; thus its PR and QRS complexes are normal on the electrocardiogram, but there is a tendency to develop premature supraventricular tachycardia. If atrial fibrillation develops, conduction will proceed across the atrioventricular node.
Embden-Meyerhof pathway the series of enzymatic reactions in the anaerobic conversion of glucose to lactic acid, resulting in energy in the form of adenosine triphosphate (ATP).
extrinsic pathway of coagulation the mechanism that produces fibrin following tissue injury, beginning with formation of an activated complex between tissue factor and factor vii and leading to activation of factor x, which induces the reactions of the common pathway of coagulation. See also intrinsic pathway of coagulation.
final common pathway
1. the motor neurons by which nerve impulses from many central sources pass to a muscle or gland in the periphery.
2. any mechanism by which several independent effects exert a common influence.
intrinsic pathway of coagulation a sequence of reactions leading to fibrin formation, beginning with the contact activation of factor xii. This is followed by the sequential activation of factors xi and ix, which results in the activation of factor x. Activated factor X (factor Xa) initiates the common pathway of coagulation. See also extrinsic pathway of coagulation.
pentose phosphate pathway a pathway of hexose oxidation in which glucose-6-phosphate undergoes two successive oxidations by NADP, the final forming a pentose phosphate.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

pen·tose phos·phate path·way

a secondary pathway for the oxidation of d-glucose (not occurring in skeletal muscle), generating reducing power (NADPH) in the cytoplasm and synthesizing pentoses and a few other sugars. It also provides a means of converting pentoses and certain other sugars into intermediates of the glycolytic pathway. It proceeds from d-glucose 6-phosphate to d-ribulose and d-ribose phosphates, thence (with d-xylulose 5-phosphate) to d-sedoheptulose 7-phosphate and d-glyceraldehyde 3-phosphate; carbon dioxide is released in the gluconate-ribulose step. In plants, it participates in the formation of d-glucose from carbon dioxide in the dark reactions of photosynthesis. This pathway is defective in certain inherited diseases, for example, glucose-6-phosphate dehydrogenase deficiency.
Farlex Partner Medical Dictionary © Farlex 2012

pen·tose phos·phate path·way

(pen'tōs fos'fāt path'wā)
A secondary pathway for the oxidation of d-glucose (not occurring in skeletal muscle), generating reducing power (NADPH) in the cytoplasm outside the mitochondria and synthesizing pentoses and a few other sugars. This pathway is defective in certain inherited diseases (e.g., glucose-6-phosphate dehydrogenase deficiency).
Synonym(s): Dickens shunt.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

pentose phosphate pathway (PPP), pentose phosphate shunt, hexose monophosphate shunt or phosphogluronate pathway

a PATHWAY for the metabolism of glucose. PPP is particularly important in animal cells where it functions as an alternative to GLYCOLYSIS and the KREBS CYCLE, although both mechanisms occur together.

In the PPP, glucose (a hexose sugar) in the form of glucose phosphate molecules, is oxidized by the removal of hydrogen and decarboxylated, producing pentose sugars, carbon dioxide and hydrogen atoms, which are transferred to the coenzyme NADP to form NADPH2. In a second stage the pentose sugars are rearranged to produce hexose again, although in a smaller quantity than at the start. Unlike NADH, NADPH is not involved in producing ATP via an ELECTRON TRANSPORT SYSTEM, but transfers hydrogen atoms and electrons to sites where molecules are being assembled.

The NADPH2 molecules are particularly active in cells carrying out fat metabolism, such as adipose tissue, liver, adrenal cortex, mammary gland tissue.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

Dickens,

Frank, English biochemist, 1899–.
Dickens shunt - a secondary pathway for the oxidation of d-glucose (not occurring in skeletal muscle), generating reducing power in the cytoplasm outside the mitochondria and synthesizing pentoses and a few other sugars. Synonym(s): pentose phosphate pathway; Warburg-Lipmann-Dickens-Horecker shunt
Warburg-Lipmann-Dickens-Horecker shunt - Synonym(s): Dickens shunt
Medical Eponyms © Farlex 2012
References in periodicals archive ?
Clear-cell RCC cells are endowed with increased activity of the pentose phosphate pathway (PPP).[sup.20] In addition, clear-cell RCC cells have higher resistance to apoptosis, oxidative stress, and radiation compared with normal cells.
It is especially helpful for discriminating between glucose metabolism through the oxidative and nonoxidative branches of the pentose phosphate pathway (see sidebar, p.
The oxidative pentose phosphate pathway and the malate shunt also contribute flexibility (and complexity).
As such, the pentose phosphate pathway is an indispensable metabolic pathway in malignant tumors because of the demand for a high rate of nucleic acid synthesis during growth and the NADPH necessary for cell survival during oncogenic cellular stress.
It has been shown to regulate glucose utilization and enhance flux of glucose into the pentose phosphate pathway and preserve cellular glutathione (GSH) levels.
Nrf2 regulates the protein turnover by inducing proteasome subunits to confer protective effects against chronic diseases [4] and modifies cellular metabolic processes, for example, the pentose phosphate pathway, which provides NADPH and purine nucleotides that are essential for the redox homeostasis and cellular proliferation [5,6].
Yellow color marked pathway is the pentose phosphate pathway; the number in parenthesis is the gene copy found in the genome; GalK: galactokinase (EC 2.71.6); GalE: UDP-glucose 4-epimerase (EC 5.1.3.2); GalT: UDP-glucose-hexose-1-phosphate uridylyltransferase (EC 2.7.7.12); GalU: UTP-glucose-1- phosphate uridylyltransferase (EC 2.7.79); PGM: phosphoglucomutase (EC 5.4.2.2); XI: xylose isomerase (EC 5.3.1.5); XK: xylulokinase (EC 2.71.17); AI: arabinose isomerase (EC 5.3.1.4); RK: ribulokinase (EC 2.71.16); RI: ribose 5-phosphate isomerase (EC 5.3.1.6); RPE: ribulose-phosphate 3-epimerase (EC 5.1.3.1); TKL: transketolase (EC 2.2.1.1); TAL: transaldolase (EC 2.2.1.2).
SD principally resulted in the decrease of metabolites of glycolysis, pentose phosphate pathway (PPP), branched chain amino acids (BCAA, including valine, leucine, and isoleucine), tyrosine, and the amino acids related to potential antioxidation (cysteine, threonine, serine, methionine, and 4-hydroxyproline) and the increase of fat metabolism derivatives (glycerol 3-phosphate and 3-hydroxybutyric acid) and neurotransmitter (glutamic acid and aspartic acid) in the brain.
It generates the reducing equivalent NADPH for anabolism and ribose 5-phosphate for nucleotide synthesis via the pentose phosphate pathway [26].
This may be done by the activation of reductive pentose phosphate pathway (PPP) by high-dose thiamine therapy that would increase transketolase (TK) activity and stimulate the conversion of glyceraldehyde-3-phosphate (GA3P) and fructose-6-phosphate (F6P) to ribose-5-phosphate (R5P), thus reducing the risk of the development of diabetic complications.
In this approach, we block three of the metabolic pathways in the cancer cell: (1) the efflux of lactic acid, (2) glutamine use, and (3) the pentose phosphate pathway (an alternative to glycolysis).
The activity of glucose-6-phosphate dehydrogenase was decreased which slows clown the pentose phosphate pathway in diabetic conditions (Abdel-Rahim et al.