A. Relimpio, J. C. Slebe, M. Martinez-Carrión
Apr 7, 1975
Citations
0
Influential Citations
13
Citations
Journal
Biochemical and biophysical research communications
Abstract
Trifluoromethionine and p and o -monofluorophenylalanine can be accepted by cytoplasmic aspartate transaminase as substrates; α-trifluoromethyl-DL-alanine can act as an inhibitor of the enzyme. Covalent pyridoxal phosphate (PLP) derivatives of these amino acids can be prepared and after reduction of the resulting Schiff's base with NaBH4 the isolated PLP-fluorinated amino acids used as inhibitors of apoenzyme. The union of the fluorinated-PLP compounds to apoenzyme is stoichiometric as judged by fluorescence and circular dichroism techniques as well as by inhibition of enzymatic transamination with the natural substrates, aspartate and α-ketoglutarate. The transaminase retains its stereospecific discrimination at the substrate level and when presented with a racemic mixture of fluorinated (DL) amino acid-PLP compound accepts only one isomer. The holoenzyme-fluorinated substrate complexes are stable to dialysis and chromatography through Sephadex G-25, yet, they can be resolved by phosphate buffers into native apoenzyme and fluorinated amino acid-PLP compound.