PURIFICATION AND PROPERTIES OF AN LD-DIPEPTIDASE FROM BACILLUS-SPHAERICUS

1. 1. An ld-dipeptidase (EC 3.4.13.-) that hydrolyzes the unrelated dipeptides l-Ala-d-Glu (sp. act. 0.85 μmol·min-1·mg-1) and l-Lys-d-Ala (sp. act. 11 μmol · min-1·mg-1) has been purified 250-fold from the sporulation medium of Bacillus sphaericus with a 4% recovery of lytic activity. 2. 2. Throughout the purification steps, followed with both substrates, the enzyme peaks of activities were congruent and the ratios of activities were constant. Both activities were activated 50-fold by cobalt. Polyacrylamide gel electrophoresis of the final preparation showed the two enzyme activities to be coincident. The data are consistent with those activities being due to a single enzyme. 3. 3. Sodium dodecylsulfate polyacrylamide gel electrophoresis of the purified enzyme showed a single protein band (Mr 38,000). 4. 4. This dipeptidase hydrolyzes some other ld-dipeptides with a free amino and carboxyl group. Although dipeptides having a di-amino acid as the amino terminus are the best of the substrates tested, the hydrolysis occurs also when neutral amino acids are N-terminal. The activity is higher with neutral C-terminal residues such as Gly or d-Ala than with a di-acid residue such as d-Glu. 5. 5. This enzyme may have a function in peptidoglycan metabolism. © 1990.