Distribution of lysine racemase in bacteria.

We have reported elsewhere the racemization of lysine by cell preparations of Proteus vulgaris strain ATCC 4669 (Huang et al., 1958). The simplest explanation of the results presented is that Proteus vulgaris contains a lysine racemase. The distribution of this activity in bacteria has now been investigated. Almost a hundred species, from eleven families, have been examined. Only nine species, all from the genera Proteus and Escherichia, could be shown to catalyze the racemization of lysine. We have also examined the effect of Proteus vulgaris on alanine, glutamic acid and methionine. Only alanine was found to be racemized to an appreciable extent.