Positive heterotropic allosteric regulation

Fig. 4 Positive heterotropic allosteric regulation of complexation with calixarene hosts. Entry 12 Reprinted from Ref. [23]. Copyright 1998. with permission from Elsevier Entry 13 Reprinted with permission from Ref. [5]. Copyright 2001 by American Chemical Society Entry 14 Reprinted from Ref. [24]. Copyright 2000, with permission from Elsevier.

Relationship between the initial velocity (v) and the substrate concentration [S] for an allosteric enzyme that shows a heterotropic effect with constant Vmax but with varying ATq.s- Curve a is obtained in the absence of any modulators, curve b in the presence of a positive modulator, and curve c in the presence of a negative modulator. Regulation is achieved by modulation of ATq.s without change in F ax. 

Many proteins are regulated by molecules which bind somewhere other than at the active site and either inerease or decrease protein activity. These allosteric ejfectors are often quite specific and may have either a positive or negative effect upon protein activity. C ass cdX feedback inhibition cycles in metabolism generally involve heterotropic allostery, in which a molecule produced near the end of a metabolic pathway acts as an allosteric effector to regulate a protein active earlier in the same pathway. Because of the need for very precise control of the energy charge of the cell, ATP and ADP serve as allosteric effectors for several of the proteins of glucose metabolism. Protons and ions act as allosteric effectors in many... 

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