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Allosteric enzymes need not be oligomers as previously thought, [1] and in fact many systems have demonstrated allostery within single enzymes. [2] In biochemistry , allosteric regulation (or allosteric control ) is the regulation of a protein by binding an effector molecule at a site other than the enzyme's active site .
Allosteric regulation of an enzyme. In the fields of biochemistry and pharmacology an allosteric regulator (or allosteric modulator) is a substance that binds to a site on an enzyme or receptor distinct from the active site, resulting in a conformational change that alters the protein's activity, either enhancing or inhibiting its function.
A simplified reaction mechanism for N-acetylglutamate synthase (NAGS). Two mechanisms for N-acetyltransferase function have been proposed: a two-step, ping-pong mechanism involving transfer of the relevant acetyl group to an activated cysteine residue [10] and a one-step mechanism through direct attack of the amino nitrogen on the carbonyl group. [11]
In a) the allosteric enzyme functions normally. In b), it is inhibited. This type of enzymes presents two binding sites: the substrate of the enzyme and the effectors. Effectors are small molecules which modulate the enzyme activity; they function through reversible, non-covalent binding of a regulatory metabolite in the allosteric site (which ...
In microbes, the activity is controlled by the concentration of ammonium and or the like-sized rubidium ion, which binds to an allosteric site on GLDH and changes the K m (Michaelis constant) of the enzyme. [9] The control of GLDH through ADP-ribosylation is particularly important in insulin-producing β cells.
This enzyme's main function is to synthesize or degrade allosteric regulator Fru-2,6-P 2 in response to glycolytic needs of the cell or organism, as depicted in the accompanying diagram. PFK-2 and FBPase-2 Reaction. In enzymology, a 6-phosphofructo-2-kinase (EC 2.7.1.105) is an enzyme that catalyzes the chemical reaction:
In this manner, effector molecules act as ligands that can increase or decrease enzyme activity, gene expression, influence cell signaling, or other protein functions. An example of such an effector is oxygen, which is an allosteric effector of hemoglobin - oxygen binding to one of the four hemoglobin subunits greatly increases the affinity of ...
Because malate dehydrogenase is closely tied to the citric acid cycle, studies have proposed and experimentally demonstrated that citrate is an allosteric regulator of malate dehydrogenase depending on the concentrations of L-malate and NAD +. This may be due to deviations observed in the kinetic behavior of malate dehydrogenase at high ...