THE RELATION OF D-ALANINE AND ALANINE RACEMASE ACTIVITY IN MOLLUSKS

1. Eighteen molluscan species were examined for the presence Of D-alanine and alanine racemase activity to probe the probable relation between them. 2. Two bivalve species had high concentrations of D-alanine and L-alanine (1:1) and showed high activities of alanine racemase. In these species, the occurrence of D-alanine could be explained by the action of alanine racemase. 3. In other species, the levels Of D-alanine and enzyme activity were low, and the occurrence Of D-alanine did not correspond with the presence of alanine racemase activity. 4. The mechanism of the occurrence Of D-alanine in molluscan tissues seems to vary from species to species and seems not to be associated with the phylogenic situation or habitats of the respective species.