代謝経路、代謝系、代謝過程、代謝パスウェイ

関: metabolic network、metabolic process

WordNet

of or relating to metabolism; "metabolic rate"
undergoing metamorphosis (同)metabolous
a trodden path (同)footpath

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新陳代謝の
道,小道(path)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/10/15 05:26:44」(JST)

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In biochemistry, metabolic pathways are series of chemical reactions occurring within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function properly. Because of the many chemicals (a.k.a. "metabolites") that may be involved, metabolic pathways can be quite elaborate. In addition, numerous distinct pathways co-exist within a cell. This collection of pathways is called the metabolic network. Pathways are important to the maintenance of homeostasis within an organism. Catabolic (break-down) and Anabolic (synthesis) pathways often work interdependently to create new biomolecules as the final end-products.

A metabolic pathway involves the step-by-step modification of an initial molecule to form another product. The resulting product can be used in one of three ways:

To be used immediately,
To initiate another metabolic pathway, called a flux generating step
To be stored by the cell

A molecule called a substrate enters a metabolic pathway depending on the needs of the cell and the availability of the substrate. An increase in concentration of anabolic and catabolic intermediates and/or end-products may influence the metabolic rate for that particular pathway.

Overview[edit]

Each metabolic pathway consists of a series of biochemical reactions that are connected by their intermediates: the products of one reaction are the substrates for subsequent reactions, and so on. Metabolic pathways are often considered to flow in one direction. Although all chemical reactions are technically reversible, conditions in the cell are often such that it is thermodynamically more favorable for flux to flow in one direction of a reaction. For example, one pathway may be responsible for the synthesis of a particular amino acid, but the breakdown of that amino acid may occur via a separate and distinct pathway. One example of an exception to this "rule" is the metabolism of glucose. Glycolysis results in the breakdown of glucose, but several reactions in the glycolysis pathway are reversible and participate in the re-synthesis of glucose (gluconeogenesis).

Glycolysis was the first metabolic pathway discovered:

As glucose enters a cell, it is immediately phosphorylated by ATP to glucose 6-phosphate in the irreversible first step.
In times of excess lipid or protein energy sources, certain reactions in the glycolysis pathway may run in reverse in order to produce glucose 6-phosphate which is then used for storage as glycogen or starch.

Metabolic pathways are often regulated by feedback inhibition.
Some metabolic pathways flow in a 'cycle' wherein each component of the cycle is a substrate for the subsequent reaction in the cycle, such as in the Krebs Cycle (see below).
Anabolic and catabolic pathways in eukaryotes often occur independently of each other, separated either physically by compartmentalization within organelles or separated biochemically by the requirement of different enzymes and co-factors.

Major metabolic pathways[edit]

Glucuronate metabolism

Pentose interconversion

Inositol metabolism

Cellulose and sucrose
metabolism

Starch and glycogen
metabolism

Other sugar
metabolism

Pentose phosphate pathway

Glycolysis and Gluconeogenesis

Amino sugars metabolism

Small amino acid synthesis

Branched amino acid
synthesis

Purine biosynthesis

Histidine metabolism

Aromatic amino
acid synthesis

Pyruvate
decarboxylation

Fermentation

Fatty acid
metabolism

Urea cycle

Aspartate amino acid
group synthesis

Porphyrins and

corrinoids

metabolism

Citric acid cycle

Glutamate amino

acid group

synthesis

Pyrimidine biosynthesis

	All pathway labels on this image are links, simply click to access the article.
	A high resolution labeled version of this image is available here.

Cellular respiration[edit]

Main article: Cellular respiration

Several distinct but linked metabolic pathways are used by cells to transfer the energy released by breakdown of fuel molecules into ATP and other small molecules used for energy (e.g. GTP, NADPH, FADH).

These pathways occur within all living organisms in some form:

Glycolysis
Aerobic respiration and/or Anaerobic respiration
Citric acid cycle / Krebs cycle (not in most obligate anaerobic organisms)
Oxidative phosphorylation (not in obligate anaerobic organisms)

Synthesis of energetic compounds from non-living matter:

Photosynthesis (plants, algae, cyanobacteria)

External links[edit]

BioCyc: Metabolic network models for thousands of organisms
KEGG: Kyoto Encyclopedia of Genes and Genomes
Reactome, a database of reactions, pathways and biological processes
MetaCyc: A database of non-redundant, experimentally elucidated metabolic pathways (2,100+ pathways from more than 2,500 different organisms).
The Pathway Localization database (PathLocdb)
Metabolism, Cellular Respiration and Photosynthesis - The Virtual Library of Biochemistry and Cell Biology
Interactive Flow Chart of the Major Metabolic Pathways
A novel visualization for a Metabolic Pathway
DAVID: Visualize genes on pathway maps
Wikipathways: pathways for the people
ConsensusPathDB

UpToDate Contents

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1. 先天性代謝異常：代謝性救急疾患 inborn errors of metabolism metabolic emergencies
2. 代謝性ミオパチーへのアプローチ approach to the metabolic myopathies
3. 空腹時ケトアシドーシスおよびアルコール性ケトアシドーシス fasting ketosis and alcoholic ketoacidosis
4. 先天性代謝異常：疫学、病因、および臨床的特徴 inborn errors of metabolism epidemiology pathogenesis and clinical features
5. ポルフィリン症：概要 porphyrias an overview

English Journal

Autophagy induction by tetrahydrobiopterin deficiency.

Kwak SS, Suk J, Choi JH, Yang S, Kim JW, Sohn S, Chung JH, Hong YH, Lee DH, Ahn JK, Min H, Fu YM, Meadows GG, Joe CO.SourceDepartment of Biological Sciences; Korea Advanced Institute of Science and Technology; Daejeon, South Korea.
Autophagy.Autophagy.2011 Nov 1;7(11). [Epub ahead of print]
Tetrahydrobiopterin (BH 4) deficiency is a genetic disorder associated with a variety of metabolic syndromes such as phenylketonuria (PKU). In this article, the signaling pathway by which BH 4 deficiency inactivates mTORC1 leading to the activation of the autophagic pathway was studied utilizing BH
PMID 21795851

Metabolic regulation by HMGB1-mediated autophagy and mitophagy.

Kang R, Livesey KM, Zeh HJ 3rd, Loze MT, Tang D.SourceThe DAMP Laboratory; Department of Surgery; Hillman Cancer Center; University of Pittsburgh Cancer Institute; University of Pittsburgh; Pittsburgh, PA USA.
Autophagy.Autophagy.2011 Oct 1;7(10). [Epub ahead of print]
Autophagy is a dynamic process for degradation of cytosolic components such as dysfunctional organelles and proteins and a means for generating metabolic substrates during periods of starvation. Mitochondrial autophagy ("mitophagy") is a selective form of autophagy, which is important in maintaining
PMID 21691146

Japanese Journal

糖尿病とミトコンドリア機能

尾形真規子
東京女子医科大学雑誌 81(E2), E85-E88, 2011-03-31
糖尿病はインスリン分泌能の低下とインスリン抵抗性により高血糖が起きる疾患群である。膵β細胞存続にミトコンドリア機能が重要であり、また、発症後の高血糖によるミトコンドリア遺伝子の脆弱性から、標的臓器の二次的な障害にミトコンドリア障害が関与する可能性が指摘されていた。1990年代に入り、ミトコンドリア遺伝子異常症による糖尿病が報告され、糖尿病の発症という観点からミトコンドリア機能異常が注目されている。 …
NAID 110008441449

A novel L-isoleucine metabolism in Bacillus thuringiensis generating (2S,3R,4S)-4-hydroxyisoleucine, a potential insulinotropic and anti-obesity amino acid.

Ogawa Jun,Kodera Tomohiro,Smirnov Sergey V,Hibi Makoto,Samsonova Natalia N,Koyama Ryoukichi,Yamanaka Hiroyuki,Mano Junichi,Kawashima Takashi,Yokozeki Kenzo,Shimizu Sakayu
Applied microbiology and biotechnology 89(6), 1929-1938, 2011-03
… thuringiensis ATCC 35646 operate a novel metabolic pathway for L-isoleucine (L-Ile) via HIL and 2-amino-3-methyl-4-ketopentanoic acid (AMKP). … The metabolic pathway functions as an effective bypass pathway that compensates for the incomplete tricarboxylic acid (TCA) cycle in Bacillus species and also explains how AMKP, a vitamin B(12) antimetabolite with antibiotic activity, is synthesized. …
NAID 120003001354

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リンク元	「代謝系」「代謝過程」「metabolic process」「metabolic network」「代謝パスウェイ」
拡張検索	「metabolic pathway／metabolite flow」
関連記事	「metabolic」「pathway」