Biosynthesis of peptidoglycan in Gaffkya homari: on the target(s) of benzylpenicillin.
Biosynthesis of peptidoglycan in Gaffkya homari: on the target(s) of benzylpenicillin.
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Gaffkya homari 中肽聚糖的生物合成：针对苄青霉素的靶标。
DOI：
10.1128/aac.35.9.1753
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发表时间：
1991
影响因子：
4.9
通讯作者：
Neuhaus,FC
中科院分区：
文献类型：
--
作者：
Sinha,RK;Neuhaus,FC
N-（D-Ala）-受体转肽酶受体的形成是新生肽聚糖加工的基本特征。在Gaffkya homari中，肽聚糖中交叉桥的合成包括多种青霉素敏感酶，例如，转肽酶、DD-羧肽酶和LD-羧肽酶。为了确定主要目标，我们在青霉素（0.2微克/毫升）、甲氧西林（10微克/毫升）、头孢菌素（5微克/毫升）和头孢西丁（25微克/毫升）的MIC存在下培养培养物，并检查了每种肽聚糖的单体-二聚体组成。在溶菌酶消化后通过高效液相色谱法。从这些研究中认识到，在所有二聚体中，主要的交联桥、二酰胺化八肽（-Ala-iso-D-Gln-Lys-D-Ala-Ala-iso-D-Gln-Lys-D-Ala）的合成对β-内酰胺在其MIC下的作用最敏感。受体四肽（转肽酶的底物之一）的增强脱酰胺作用与此交叉桥的抑制相关。例如，在苄青霉素的MIC下，酰胺化四肽与非酰胺化四肽的比率从对照中的2.8降低到处理培养物中的1.0。从这些结果看来，转肽酶的优选受体的减少导致该主要交叉桥的合成的抑制。因此，单体肽的酰胺官能团的代谢可能代表了该生物体肽聚糖中交联二聚体组装过程中的额外加工特征，该生物体对β-内酰胺的作用敏感。
The formation of acceptor for the N epsilon-(D-Ala)-acceptor transpeptidase is an essential feature of nascent peptidoglycan processing. In Gaffkya homari the synthesis of cross-bridges in peptidoglycan includes a variety of penicillin-sensitive enzymes, e.g., transpeptidase, DD-carboxypeptidase, and LD-carboxypeptidase. To determine the primary target, we grew cultures in the presence of the MICs of benzylpenicillin (0.2 microgram/ml), methicillin (10 micrograms/ml), cephalothin (5 micrograms/ml), and cefoxitin (25 micrograms/ml) and examined the monomer-dimer composition of each peptidoglycan by high-performance liquid chromatography after muramidase digestion. From these studies it was recognized that of all the dimers, the synthesis of the predominant cross-bridge, diamidated octapeptide (-Ala-iso-D-Gln-Lys-D-Ala -Ala-iso-D-Gln-Lys-D-Ala), is most sensitive to the action of the beta-lactam at its MIC. The enhanced deamidation of the acceptor tetrapeptide, one of the substrates for the transpeptidase, is correlated with the inhibition of this cross-bridge. For example, at the MIC of benzylpenicillin, the ratio of amidated tetrapeptide to nonamidated tetrapeptide decreased from 2.8 in the control to 1.0 in the treated culture. From these results it would appear that a decrease in preferred acceptor for the transpeptidase results in the inhibition of synthesis of this major cross-bridge. Thus, the metabolism of the amide function of the monomer peptides may represent an additional feature of processing in the assembly of cross-bridged dimers in the peptidoglycan of this organism that is sensitive to the action of beta-lactam.