title: Structural basis for the entrance into the phenylpropanoid metabolism catalyzed by phenylalanine ammonia-lyase.
abstract: 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.
authors.affiliation: Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Freiburg im Breisgau, Germany 79104.
authors.forename: Holger
authors.initials: H
authors.lastname: Ritter
authors.forename: Georg E
authors.initials: GE
authors.lastname: Schulz
mesh_terms: D000595:Amino Acid Sequence / Q000502:physiology; D000641:Ammonia / Q000378:metabolism; D002384:Catalysis; D020134:Catalytic Domain / Q000502:physiology; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008967:Molecular Biology; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D028528:Petroselinum / Q000737:chemistry / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism; D010650:Phenylalanine Ammonia-Lyase / Q000737:chemistry* / Q000378:metabolism*; D010666:Phenylpropionates / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology
chemical_list: D010666:Phenylpropionates; D010649:Phenylalanine; D000641:Ammonia; D010650:Phenylalanine Ammonia-Lyase