Restricted intramolecular energy flow in the enzyme-substrate complex.

The fate of the energy released during the formation of the enzyme-substrate complexes is discussed in connection with energetic aspects of the one-substrate enzyme-catalysed reaction. Assuming a free and rapid intramolecular energy flow in the complex, the high enzyme catalytic activity cannot be explained. It is suggested that a metal ion near the active site can serve as a barrier to the energy flow from the binding sites of the complex into the enzyme molecule. The effective vibrational temperature of the bonded substrate molecule is then higher than the temperature of the reaction system.