Allosteric enzyme

Regulatory enzyme

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synonym Allosteric enzyme (allosteric enzyme) generally refers to allosteric enzyme

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When certain compounds and enzymes Allosteric site After reversible binding, the enzyme Molecular conformation Change enzymatic activity Position pair substrate The combination of Catalysis Affected to adjust Enzymatic reaction Speed and metabolic process, this effect is called Allosteric effect 。 The enzyme with allosteric effect is called allosteric enzyme. Allosteric enzymes are often Metabolic pathway It catalyzes the first step reaction or is in the metabolic pathway Branch point Class on Regulatory enzyme Most of them can be inhibited by metabolic end products and play an important role in metabolic regulation. The substance whose allosteric effect increases the activity of enzyme is called allosteric modulator And vice versa Allosteric inhibitor 。 The relationship between the initial rate of allosteric enzyme catalyzed reaction and substrate concentration does not obey Mieman's equation, but presents an S-shaped curve.

Chinese name: Allosteric enzyme
Foreign name: allosteric enzyme

Field: Chemistry, Biology
Chemical essence: protein

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Basic definitions

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Allosteric enzyme is a regulating enzyme, Specificity Of metabolite Allosteric Active site Other sites are not Covalent After combination, its activity can be adjusted.

Biological significance

Allosteric enzyme is enzymatic activity The important way of regulation is sensitive, fast and reversible key enzyme Frequently used Allosteric regulation , which can adapt to Rapid change Of environment condition .

Basic structure

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Allosteric enzymes are mostly Oligomerase , containing two or more subunits. There are two centers in its molecule: one is with substrate Binding and catalytic substrate reaction active center ； The other is with Regulator Combination and adjustment reaction rate The other structure center of. Two centers may be located at the same Subunit It may also be located on different subunits. In the latter case, the subunit with allosteric center is called Regulatory subunit 。 Allosteric enzyme changes the activity of enzyme through the conformational change of enzyme molecule itself.

chemical reaction

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Regulator Also called Effector or Regulatory factor 。 It is generally enzymatic substrate 、 Substrate analogue Or metabolic end products. After binding with allosteric center, the regulator induces or stabilizes some enzyme molecule conformation , make Active center of enzyme Binding and Catalysis Is affected, thereby Regulatory enzyme Of reaction rate And metabolic process, this effect is called enzymatic Allosteric effect （allosteric effect ）。 Caused by other structures enzyme activity Elevated substances, called Positive effector or Allosteric activator And vice versa Negative effector or Allosteric inhibitor 。 Different allosteric enzymes have different regulators. For some allosteric enzymes, the regulator molecule is the substrate molecule. There are more than two binding centers with the substrate on the enzyme molecule, and its regulation depends on how many substrate binding centers are occupied in the molecule. Allosteric enzyme reaction Initial velocity The relationship with substrate concentration (V vs [S]) is not obeyed Michaelis equation 。 Instead, it presents an S-shaped curve. The S-shaped curve shows that the activity of one functional site on the enzyme molecule affects the activity of another functional site, indicating that synergistic effect (cooperative effect), when the substrate or Effector Once combined with enzyme Molecular conformation This altered conformation greatly improves the affinity of the enzyme to subsequent substrate molecules. Results The slight change of substrate concentration can lead to Enzymatic reaction A dramatic change in speed.

Aspartate carbamoylase (Aspartate transcarbamoylase ATCase) is the most clearly understood individual enzyme. It catalyzes Pyrimidine nucleotide N – ammonia, the first intermediate in the synthesis route Formyl Aspartate And ATCase is subject to Metabolic pathway End products of CTP Of Allosteric inhibition 。 ATCase consists of two Trimer Constitutive Catalytic subunit (C3) and three Dimer Constitutive Regulatory subunit (r2) composition. When the catalytic subunit and the regulatory subunit are mixed, they can combine rapidly.

CTP's inhibitor Impact ATP The activation of and the synergistic binding substrate are affected by Four level structure Is regulated by the huge change of the catalytic subunit and the regulatory subunit Allosteric effect 。

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