Enthalpy-driven binding

Many isolated catalytic domains are less stable than the holoenzyme from which they are derived, and indeed CBM 22 was first identified as a thermo-stabilizing domain, rather than by its true function of enthalpy-driven binding of xylan and xylan oligosaccharides." ... 

The enthalpy and entropy of binding can be determined experimentally, as, for example, by isothermal titration calorimetry (46,471. These data, however, are still sparse and not always easy to interpret (48, 49). Substantial compensation between enthalpic and entropic contributions is observed (50-52) this phenomenon and its interpretations have recently been critically reexamined (53). Interestingly, the data also show that binding can be both enthalpy-driven (e.g., streptavidin-biotin, AG = -76.5 kJ/mol, AH = -134 kJ/mol) or entropy-driven (e.g., streptavidin-HABA, AG = -22.0 kJ/mol, AH = +7.1 kJ/mol) (54). However, because cf strong temperature dependencies, even this partitioning is a question of the temperature used for measuring. 

The consequences are seen in Figure 17.1, the agonists ( ) are binding to the (3-receptors by an enthalpy-driven process, whereas the antagonists (O) are binding with entropy and/or enthalpy-entropy driven processes. 

Notable Type C CBMs are the CBM Family 9 (p-sandwich folded),one member of which has been shown rigorously to bind the reducing end of oligo-and polysaccharides in an enthalpy-driven process." ... 

CBM Family 13 adopt the p-trefoil fold first encountered with the ricin B (carbohydrate-binding) chain. It contains 12 strands of p-sheet arranged in such a way as to provide three independent sugar binding sites with different specificities, and again binding is enthalpy driven. 

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