Editing Metabolic pathway (section)

==Regulation==

The flux of the entire pathway is regulated by the rate-determining steps.<ref name="Nelson"/>{{rp|577–578}} These are the slowest steps in a network of reactions. The rate-limiting step occurs near the beginning of the pathway and is regulated by feedback inhibition, which ultimately controls the overall rate of the pathway.<ref>{{cite book| veditors = Kruger NJ | vauthors = Hill SA, Ratcliffe RG |title=Regulation of primary metabolic pathways in plants : [proceedings of an international conference held on 9 - 11 January 1997 at St Hugh's College, Oxford under the auspices of the Phytochemical Society of Europe] |date=1999|publisher=Kluwer|location=Dordrecht [u.a.]|isbn=978-0-7923-5494-9 |pages=258}}</ref> The metabolic pathway in the cell is regulated by covalent or non-covalent modifications. A covalent modification involves an addition or removal of a chemical bond, whereas a non-covalent modification (also known as allosteric regulation) is the binding of the regulator to the enzyme via [[hydrogen bond]]s, electrostatic interactions, and [[Van der Waals force]]s.<ref>{{cite book| vauthors = White D |title=The physiology and biochemistry of prokaryotes|date=1995|publisher=Oxford Univ. Press|location=New York [u.a.]|isbn=978-0-19-508439-9 |pages=133}}</ref>

The rate of turnover in a metabolic pathway, also known as the [[Flux (metabolism)|metabolic flux]], is regulated based on the stoichiometric reaction model, the utilization rate of metabolites, and the translocation pace of molecules across the [[lipid bilayer]].<ref name="Weckwerth">{{cite book|title=Metabolomics methods and protocols|date=2006|publisher=Humana Press|isbn=978-1-59745-244-1 |location=Totowa, N.J.|pages=177| veditors = Weckwerth W }}</ref> The regulation methods are based on experiments involving [[Carbon-13|13C-labeling]], which is then analyzed by [[Nuclear magnetic resonance spectroscopy|nuclear magnetic resonance (NMR)]] or [[Gas chromatography–mass spectrometry|gas chromatography–mass spectrometry (GC–MS)]]–derived mass compositions. The aforementioned techniques synthesize a statistical interpretation of mass distribution in [[proteinogenic amino acid]]s to the catalytic activities of enzymes in a cell.<ref name="Weckwerth"/>{{rp|178}}