PURIFICATION AND PROPERTIES OF THE EXOCELLULAR BETA-LACTAMASE OF ACTINOMADURA STRAIN R39
PURIFICATION AND PROPERTIES OF THE EXOCELLULAR BETA-LACTAMASE OF ACTINOMADURA STRAIN R39
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DOI：
10.1016/0167-4838(82)90287-4
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发表时间：
1982-01-01
期刊：
影响因子：
--
通讯作者：
DIERICKX, L
中科院分区：
文献类型：
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作者：
DUEZ, C;FRERE, JM;DIERICKX, L
The exocellular .beta.-lactamase (penicillin amido-.beta.-lactamhydrolase, EC 3.5.2.6) of Actinomadura R39 consists of 1 single polypeptide chain of MW .apprx. 15,200. It exhibits a highly asymmetrical shape, has a low isoelectric point (at pH 5.0) and contains .apprx. 9.3% (wt/wt) of a polydeoxyribonucleotide with which it forms a rather stable complex. Removal of a substantial amount of this deoxyribonucleotide by treatment with DNAase I has no effect on the enzyme activity. The .beta.-lactamase has a wide spectrum of activity. Penicillins and .DELTA.3-cephalosporins can be good or poor substrates. Oxacillin, which is a poor substrate of most .beta.-lactamases from gram-positive bacteria, is a good substrate of the .beta.-lactamase of Actinomadura R39. Its best substrate is nitrocefin (kcat/Km: 2,300,000 M-1 .cntdot. s-1; catalytic center activity: 210 s-1). The kcat/Km values observed with some penicillins and .DELTA.3-cephalosporins are similar to the values of the bimolecular rate constants that govern the formation of the acyl-enzyme intermediates between these antibiotics and the serine D-alanyl-D-alanine peptidase that is also secreted by the same strain Actinomadura R39. Such a relationship is not observed with all the .beta.-lactam compounds tested.
