Abstract

D-Cycloserine is a competitive inhibitor of alanine racemase for which its K_i is 100 times smaller than the K_m for either of the substrates, D- and L-alanine. L-Cycloserine, however, does not inhibit this enzyme. A hypothesis is proposed, based on molecular models, that D-cycloserine has the conformation required of the substrates on the enzyme surface. L-Cycloserine cannot have this conformation.