對於一些細菌所產生的毒素，經由作用於眞核細胞内某些重要蛋白質的核苷核糖化反 應（ADP-ribosylating reaction)而影響其正常的生理功能已有大致的了解.°大部份這類的毒素 主要是由兩個部份（moieties)，A和B所组成D B部份負責其分子本身與毒性敏感細胞表面 特殊受器的結合，而A部份則負責執行核苷核糖化（ADP-ribosylate)細胞内蛋白質的酵素活 性。綠腺桿菌外毒素A_ (Pseudomojias exotoxin A，簡稱PEA) ’是綠腺样菌所產生的細胞外 產物中最具毒性的成份。此一外泌性蛋白質毒素主要由三個區域（domains )所组成：即區 域I，區城II和區域m，其主要功能分別與細胞的結合（binding )、在細胞内的移位 (translocation)和發揮核苷核糖化活性（ADP-ribosylating activity)有關。吾人若應用綠朦桿 菌外毒素A之核苷核糖化反應毒殺細胞的功能，一般皆相信可以作爲製備免疫毒素 (immunotoxins)的最佳選撣。在本篇综論中，吾人將討論核苷核糖化細菌毒素（ADP-ribosy-lating bacterial toxin)的結構、作用機制，並對於綠膿桿菌外毒素A，以及綠膿桿菌外毒素A 和其他核苷核糖化毒素（ADP-ribosylating toxin)的異同作一簡介。

It is well known that a number of toxins produced by bacteria exert their action by ADP-ribosylating reaction to certain proteins which are essential for normal eukaryotic cellular functions. Most of these toxins are composed of two moieties, A and B. The B moiety mediates the binding to the specific receptor on the surface of toxin-sensitive cells, while the A moiety is responsible for the enzymatic ADP-ribosylating activity. Pseudomonas exotoxin A (PEA) is the most toxic component of the extracellular products produced by Pseudomonas aeruginosa. The three domain model of PEA has been well established : domain I, domain II, and domain III exerting binding, translocation, and ADP-ribosylating activities, respectively. Because of the cytotoxic ADP-ribosylating nature of PEA, it has been suggested as a good candidate in the preparation of immunotoxins. In this minireview article, we discuss the structure and function of the bacterial ADP-ribosylating toxins including PEA and compare the differences particularly between PEA and other valevant toxins.