Sans N, Schröder G, Schröder J
Eur J Biochem. 1987 Aug 17;167(1):81-7. doi: 10.1111/j.1432-1033.1987.tb13306.x.
Plant tumors induced by Agrobacterium tumefaciens synthesize a group of substances (opines) which can serve as sole source of carbon and nitrogen for the bacteria. We investigate Ti-plasmid-coded genes and enzymes involved in catabolism of the opine N2-(1,3-dicarboxypropyl)-L-arginine (nopaline) with a novel approach: expression and mapping of protein-coding regions in Escherichia coli minicells, followed by identification of enzyme functions in the heterologous E. coli background. The results show that a specific part of the nopaline catabolism (Noc) region of Ti plasmid C58 is packed with closely spaced protein-coding regions which can be expressed into polypeptides of distinct sizes in E. coli. We identify and map three enzyme activities: nopaline oxidase, arginase and ornithine cyclodeaminase, an unusual protein converting ornithine directly into proline. Nopaline oxidase requires two different Noc-gene-encoded proteins for function and the latter two enzymes are new discoveries in the Noc region. These three enzyme activities together constitute a catabolic pathway leading from nopaline through arginine and ornithine to proline.
根癌农杆菌诱导产生的植物肿瘤能合成一类物质（冠瘿碱），这类物质可为细菌提供唯一的碳源和氮源。我们采用一种新方法研究了参与冠瘿碱N2-(1,3-二羧丙基)-L-精氨酸（胭脂碱）分解代谢的Ti质粒编码基因和酶：在大肠杆菌小细胞中对蛋白质编码区进行表达和定位，随后在异源大肠杆菌背景中鉴定酶的功能。结果表明，Ti质粒C58的胭脂碱分解代谢（Noc）区域的特定部分密集排列着蛋白质编码区，这些编码区在大肠杆菌中可表达为不同大小的多肽。我们鉴定并定位了三种酶活性：胭脂碱氧化酶、精氨酸酶和鸟氨酸环脱氨酶，后者是一种能将鸟氨酸直接转化为脯氨酸的特殊蛋白质。胭脂碱氧化酶的功能需要两种由不同Noc基因编码的蛋白质，后两种酶是在Noc区域的新发现。这三种酶活性共同构成了一条从胭脂碱经精氨酸和鸟氨酸到脯氨酸的分解代谢途径。
