HOW NATURE DEALS WITH STEREOISOMERS

All natural proteins are composed of L-amino acids and are inherently chiral. The properties of both L- and chemically synthesized D-amino a cids are identical except in optically asymmetric interactions. Struct ural studies of D-L racemic mixtures of crystallographic interest are discussed. The review also gives some recent examples of stereospecifi city: how L-proteins deal with L- Or D-substrates and how enzymes can function as racemases. Two particular examples of stereoselectivity ar e then discussed.