On the conformation of pyridoxal phosphate imine in solution and in aspartate-aminotransferase active site.

Abstract

The work comprises: Determination by nuclear magnetic resonance method of the conformation of the imino group of pyridoxal‐P oxime in solution. It has been found to be nearly coplanar with the aromatic ring. Theoretical calculation by the method of atom‐atom potentials of the permitted conformations of pyridoxal‐P imine and its analogs: 6‐methylpyridoxal‐P and 5′‐methylpyridoxal‐P. There have been found seven favourable conformations for pyridoxal‐P imine, some of which were prohibited in the analogs mentioned. Experimental estimation of the conformation of pyridoxal‐P imine in the active site of aspartate aminotransferase with the use of the above sterically hindered analogs and 5′‐deoxy‐5′‐carboxy‐methylenepyridoxal analog. In result, the number of the possible conformations for pyridoxal‐P imine in the active site has been reduced to a pair of symmetrical conformations.