Day A, White P J
Biochem J. 1977 Mar 1;161(3):677-85. doi: 10.1042/bj1610677.
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.
开发了一种用于检测2,6-二氨基庚二酸各异构体(内消旋体、LL-和DD-型)的酶法测定方法。2,6-二氨基庚二酸脱羧酶特异性作用于内消旋二氨基庚二酸,用于通过测压法测定该异构体。在内消旋体和LL-异构体的联合测定中,使用二氨基庚二酸脱羧酶和二氨基庚二酸差向异构酶(将LL-二氨基庚二酸转化为内消旋二氨基庚二酸)通过测压法共同测定。DD-异构体不受这两种酶的作用,通过比色法作为联合测定后剩余的二氨基庚二酸进行测定,该比色法也用于在酶处理前测定总二氨基庚二酸。联合酶还用于从化学合成的二氨基庚二酸制备纯DD-异构体。在四株巨大芽孢杆菌的细胞壁中存在二氨基庚二酸异构体混合物[每种约含75%(w/w)内消旋体、18% LL-型和7% DD-型],在两株蜡样芽孢杆菌的细胞壁中(约含85%内消旋体、8% LL-型和7% DD-型)。一株蜡样芽孢杆菌至少含有95%的内消旋二氨基庚二酸,仅含有痕量的LL-型和DD-异构体。测定大肠杆菌的肽聚糖至少含有95%的内消旋异构体。在各种不同培养基中生长后,一株巨大芽孢杆菌细胞壁中异构体的比例保持恒定。