Ritter Holger, Schulz Georg E
Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Freiburg im Breisgau, Germany 79104.
Plant Cell. 2004 Dec;16(12):3426-36. doi: 10.1105/tpc.104.025288. Epub 2004 Nov 17.
Because of its key role in secondary phenylpropanoid metabolism, Phe ammonia-lyase is one of the most extensively studied plant enzymes. To provide a basis for detailed structure-function studies, the enzyme from parsley (Petroselinum crispum) was crystallized, and the structure was elucidated at 1.7-A resolution. It contains the unusual electrophilic 4-methylidene-imidazole-5-one group, which is derived from a tripeptide segment in two autocatalytic dehydration reactions. The enzyme resembles His ammonia-lyase from the general His degradation pathway but contains 207 additional residues, mainly in an N-terminal extension rigidifying a domain interface and in an inserted alpha-helical domain restricting the access to the active center. Presumably, Phe ammonia-lyase developed from His ammonia-lyase when fungi and plants diverged from the other kingdoms. A pathway of the catalyzed reaction is proposed in agreement with established biochemical data. The inactivation of the enzyme by a nucleophile is described in detail.
由于苯丙氨酸解氨酶在次生苯丙烷类代谢中起关键作用，它是研究最为广泛的植物酶之一。为了给详细的结构-功能研究提供基础，对来自欧芹（Petroselinum crispum）的该酶进行了结晶，并以1.7埃的分辨率解析了其结构。它含有不寻常的亲电4-亚甲基-咪唑-5-酮基团，该基团来自于两个自催化脱水反应中的一个三肽片段。该酶类似于一般组氨酸降解途径中的组氨酸解氨酶，但含有另外207个残基，主要存在于一个使结构域界面刚性化的N端延伸区以及一个限制进入活性中心的插入α-螺旋结构域中。据推测，当真菌和植物与其他生物界分化时，苯丙氨酸解氨酶是由组氨酸解氨酶进化而来的。结合已有的生化数据提出了催化反应的途径。详细描述了亲核试剂对该酶的失活作用。
