Muropeptide Recycling Pathway & Beta Lactamase Induction

描述（由申请人提供）：令人惊讶的是，大肠杆菌每一代都会从其侧壁降解超过60%的胞壁蛋白（肽聚糖），并能够重新利用这些成分。这个过程被称为回收。本研究的目的是对大肠杆菌所用的各种酶进行鉴定和表征。大肠杆菌的细胞壁肽聚糖组分的再利用。回收涉及超过10种酶，这些酶似乎除了促进胞壁素组分的分解和再利用外没有其他目的。为了充分了解这一进程，仍有几个悬而未决的问题有待回答。回收途径是许多革兰氏阴性菌中β-内酰胺酶诱导所必需的，此外，我们最近观察到某些回收基因的突变导致自聚集和生物膜形成。因此，该途径在对青霉素的抗性和生物膜形成的健康相关领域中是有意义的。具体目标：目标#1：确定在不存在N-乙酰葡糖胺激酶的情况下利用N-乙酰葡糖胺的途径。我们已经实现了目标1的最初目标，即鉴定激酶基因并证明其在N-乙酰氨基葡萄糖再利用中的作用。目标#2：确定E。大肠杆菌降解脱水-N-乙酰胞壁酸。我们最近的研究结果表明，激酶和醚酶可能参与。因此，我们目前的努力旨在纯化这些活动，以确定负责这些活动的基因。目的#3：确定β-内酰胺酶的真正诱导剂。目的#4：确定抗原43的表达如何与胞壁蛋白三肽的再循环相关。抗原43引起促进生物膜形成的自聚集。缺失胞壁素肽连接酶（mpl）或胞壁素肽酰胺酶A（mpaA）导致三肽和抗原43的产生，表明可能涉及胞壁素三肽、L-Ala-γ-D-Glu-内消旋-二氨基庚二酸的积累。

DESCRIPTION (provided by applicant): Amazingly, Escherichia coli degrades over 60% of the murein (peptidoglycan) from its sidewalls each generation and is able to reutilize the components. This process is known as recycling. The goat of this research is to identify and characterize all the enzymes used by E. coli to reutilize cell wall peptidoglycan components. Recycling involves over 10 enzymes that appear to serve no other purpose than to facilitate breakdown and reutilization of murein components. Several outstanding questions remain to be answered in order to have a full understanding of the process. The recycling pathway is required for beta-lactamase induction in many Gram negative organisms and, in addition, we have recently observed that mutations in certain recycling genes result in autoaggregation and biofilm formation. Thus the pathway is of interest in the health related areas of resistance to penicillins and biofilm formation. Specific aims: Aim #1: Determine the pathway for utilization of N-acetylglucosamine in the absence of the N-acetylglucosamine kinase. We have already achieved the original goal of Aim 1, namely, Identify the kinase gene and demonstrate its role in reutilization of N-acetylglucosamine. Aim #2: Determine how E. coli degrades anhydro-N-acetylmuramic acid. Our recent results indicate that a kinase and an etherase may be involved. Hence our current efforts are aimed at purifying these activities in order to identify the genes responsible for the activities. Aim #3: Determine the true inducer of beta-lactamase. Aim #4: Determine how expression of antigen 43 is related to the recycling of murein tripeptide. Antigen 43 causes autoaggregation which facilitates biofilm formation. Deletion of either murein peptide ligase (mpl) or murein peptide amidase A (mpaA) results in production of tripeptide and antigen 43 suggesting that accumulation of the murein tripeptide, L-Ala-gamma-D-Glu-meso-diaminopimelic acid, may be involved.