Temperature-nearly-independent binding constant in several biochemical systems. The underlying entropy-driven binding mechanism and its practical significance.
Arguments are presented in this commentary to show that the model of temperature-nearly-independent binding that we proposed to rationalize the binding characteristics of beta-adrenergic antagonists (Miklavc et al., Biochem Pharmacol 40: 663-669, 1990) in fact provides a consistent interpretation of the temperature-nearly-independent binding constant in all other systems that have been reported in the literature: in the binding of coenzyme NADH to horse liver alcohol dehydrogenase and to octopine dehydrogenase and in the binding of an inhibitor to acetylcholinesterase No such consistent interpretation has been given thus far for any of these systems. It is characteristic of them that the binding takes place in a hydrophobic, sterically constrained environment. One can assume, therefore, that the underlying entropy-driven binding mechanism would reflect the existence and the properties of the steric bottleneck surrounding the binding pocket. We also explain why the temperature effects characteristic of hydrophobic interactions are not found experimentally in these systems, whereas in other, sometimes even structurally similar, systems such temperature effects are clearly present. Further work in necessary to establish more firmly the key features of the temperature-nearly-independent binding mechanism that has been disclosed through our analysis. The binding mechanism in question not only appears in important biochemical systems, but also has the interesting property of being relative unaffected by smaller structural changes.
Miklavc
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National Institute of Chemistry, Ljubljana, Slovenia.
D000110:Acetylcholinesterase / Q000378:metabolism*; D000319:Adrenergic beta-Antagonists / Q000378:metabolism*; D000426:Alcohol Dehydrogenase / Q000378:metabolism*; D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D000818:Animals; D016227:Benzoquinones / Q000378:metabolism; D001665:Binding Sites; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002800:Cholinesterase Inhibitors / Q000378:metabolism; D006736:Horses; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D009243:NAD / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D013696:Temperature
C098909:2,5-bis((3-(diethyl(2-chlorobenzyl)ammonio)propyl)amino)benzoquinone; D000319:Adrenergic beta-Antagonists; D016227:Benzoquinones; D002800:Cholinesterase Inhibitors; D000644:Quaternary Ammonium Compounds; D009243:NAD; D000426:Alcohol Dehydrogenase; D000594:Amino Acid Oxidoreductases; C021903:D-octopine dehydrogenase; D000110:Acetylcholinesterase