Transition states, standard states and enzymic catalysis

1. 1. Thermodynamic aspects of transition state theory are reviewed with particular reference to enzyme-catalysed reactions.

2. 2. Standard states must be specified when free energy changes of enzyme catalysed reactions are expressed graphically, otherwise false conclusions may be drawn.

3. 3. Enzymes cannot increase the rate of unimolecular reactions if either the transition state and ground state bind equally well to the enzyme or if the enzyme binds the ground state more tightly than the transition state. This is true even if the enzyme changes conformation during the reaction and even if the transition state is different in the presence and absence of enzyme.