Enzymic assays for isomers of 2,6-diaminopimelic acid in walls of Bacillus cereus and Bacillus megaterium.
An enzymic assay for individual isomers (meso-, LL- and DD-) of 2,6-diaminopimelate was developed. The enzyme 2,6-diaminopimelate decarboxylase specifically attacked meso-diaminopimelate and was used to measure this isomer manometrically. The meso- and LL-isomers were measured together manometrically in a coupled assay with diaminopimelate decarboxylase and diaminopimelate epimerase (which converts LL-diaminopimelate into meso-diaminopimelate). The DD-isomer was not attacked by either enzyme and was measured, as residual diaminopimelate after the coupled assay, by a colorimetric method, which was also used to measure total diaminopimelate before enzymic treatments. The coupled enzymes were also used to prepare pure DD-isomer from chemically synthesized diaminopimelate. A mixture of diaminopimelate isomers was present in walls of four strains of Bacillus megaterium [in each about 75% (w/w) meso-, 18% LL- and 7% DD-] and in walls of two strains of Bacillus cereus (about 85% meso-, 8% LL- and 7% DD-). One strain of B. cereus contained at least 95% meso-diaminopimelate, with only traces of LL- and DD-isomers. Peptidoglycan from Escherichia coli was assayed as containing at least 95% meso-isomer. The proportion of isomers in the wall of a strain of B. megaterium remained constant after growth in a variety of different media.
D000591:Amino Acid Isomerases; D000596:Amino Acids / Q000032:analysis; D001409:Bacillus cereus / Q000032:analysis*; D001410:Bacillus megaterium / Q000032:analysis*; D002262:Carboxy-Lyases; D002473:Cell Wall / Q000032:analysis; D002854:Chromatography, Paper; D003470:Culture Media; D003960:Diaminopimelic Acid / Q000032:analysis*; D007536:Isomerism; D008722:Methods; D010867:Pimelic Acids / Q000032:analysis*
D000596:Amino Acids; D003470:Culture Media; D010867:Pimelic Acids; D003960:Diaminopimelic Acid; D002262:Carboxy-Lyases; D000591:Amino Acid Isomerases