title: N-(5'-phosphopyridoxyl)glutamic acid and N-(5'-phosphopyridoxyl)-2-oxopyrrolidine-5-carboxylic acid and their action on the apoenzyme of aspartate aminotransferase.
abstract: 1. N-(5'-Phosphopyridoxyl)-l-glutamic acid (P-Pxy-Glu, compound I) is readily converted at pH3 into a substance (P-Pxy-Glp, compound II) characterized as N-(5'-phosphopyridoxyl)-2-oxopyrrolidine-5-carboxylic acid. 2. The u.v., i.r. and fluorescence spectra of P-Pxy-Glu and P-Pxy-Glp have been determined; from the u.v. spectra their pK values have been found and compared. 3. The apoenzyme of aspartate aminotransferase is rapidly and irreversibly inactivated by P-Pxy-Glu, but is inactivated more slowly by P-Pxy-Glp. The complex with P-Pxy-Glp is stable enough to be isolated, but it is slowly reactivated in the presence of excess of pyridoxal phosphate. 4. The u.v. spectrum of the complex of apoenzyme and P-Pxy-Glp suggests that it contains a hydrogen bond between the phenolic hydroxyl group and the pyrrolidone nitrogen; this specifies the conformation of most of the molecule of P-Pxy-Glp. This conformation is similar to that previously postulated for the enzyme-glutamate complex except for the side chain of glutamate. Hence both the affinity of P-Pxy-Glp for the apoenzyme and the fact that it is more easily removed than P-Pxy-Glu are explicable.
mesh_terms: D001219:Aspartate Aminotransferases / Q000037:antagonists & inhibitors*; D004586:Electrophoresis; D005453:Fluorescence; D005971:Glutamates; D007259:Infrared Rays; D046911:Macromolecular Substances; D008961:Models, Structural; D011732:Pyridoxal Phosphate; D011759:Pyrrolidines; D013057:Spectrum Analysis; D014466:Ultraviolet Rays
chemical_list: D005971:Glutamates; D046911:Macromolecular Substances; D011759:Pyrrolidines; D011732:Pyridoxal Phosphate; D001219:Aspartate Aminotransferases