title: [Interaction of spin-labeled analogues of vitamin B 6 with the active site of apotransaminase].
abstract: Spin-labeled analogues of vitamin B6: 2, 2, 6, 6-tetramethyl-N-oxylpiperydinyl-4-(5' phosphopyridoxyl)-amine (1) and 2, 2, 6, 6-tetramethyl-N-oxyl-piperydinyl-4-(pyridoxal-5')-phosphate (II) are synthesized. There analogues were shown to interact in the equimolar ratio with the active site of cytosol aspartate transaminase. It was proved by CD-titration of apotransaminase with I and II and by competition between the coenzyme and synthesized analogues. The free valency of spin-labeled coenzymes immediately disappears after interaction with the apoenzyme due to iminoxyl group reduction. The binding of I and II with the apoenzyme is accompanied by oxidation of one of the inner cysteine residues. The reactivation of the modified apoenzyme with PLP is not less than 65% of original transaminase activity. The analysis of space-filling atomic models of synthesized compounds allows to conclude that the distance between the centre of pyridine ring of the coenzyme and the modified thiol group is not more than 8 A.
mesh_terms: D001059:Apoproteins / Q000378:metabolism; D001665:Binding Sites; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D011485:Protein Binding; D011487:Protein Conformation; D011732:Pyridoxal Phosphate; D011736:Pyridoxine / Q000031:analogs & derivatives*; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet
chemical_list: D001059:Apoproteins; D011732:Pyridoxal Phosphate; D011736:Pyridoxine
vernacular_title: Vzaimodeĭstvie spin-mechenykh analogov vitamina B6s aktivnym tsentrom apotransaminazy