Enzymes perform the executive role in growth, energy conversion, and
repair of a living organism. Their activity is adjusted to their en-
vironment within the cell, being turned off, switched on, or finely
tuned by specific metabolites according to demands at the physiologi-
cal level. Each enzyme discovered in the long history of enzymology has
revealed its own individuality. Even closely related members of a family
differ in specificity, stability or regulatory properties. Despite
these, at first sight overwhelming aspects of individuality, common
factors of enzymic reactions have been recognized. Enzymes are
stereospecific catalysts even when a nonspecific process would yield the
same product. Knowledge of the detailed stereochemistry of an enzymic
reaction helps to deduce reaction mechanisms and to ob- tain insight
into the specific binding of substrates at the active site. This binding
close to catalytically competent groups is related to the enormous speed
of enzyme-catalyzed reactions. The physical ba- sis of rate-enhancement
is understood in principle and further exploit- ed in the design of
small organic receptor molecules as model enzymes. These aspects of
enzyme catalysis are discussed in Session 1. Session 2 emphasizes the
dynamic aspects of enzyme substrate inter- action. Substrate must
diffuse from solution space to the enzyme's surface. This process is
influenced and can be greatly facilitated by certain electrostatic
propterties of enzymes. The dynamic events during catalysis are studied
by relaxation kinetics or NMR techniques.