FIG. 4.

Alanine racemase activity in cell lysates. Cell lysates of wild-type mc²155 (WT), the Δalr strain DM22, and the complemented Δalr strain DM30 were prepared, and alanine racemase activity was determined. Rates are expressed in mU/mg protein where 1 unit corresponds to 1 μmol l-alanine produced per minute. Background rates in the absence of d-alanine substrate (white bars) and rates in the presence of d-alanine (striped bars) are the means of triplicate measurements, and the error bars denote standard deviations.