title: Affinity labeling of pyridoxal kinase with adenosine polyphosphopyridoxal.
abstract: Pyridoxal kinase is inactivated by preincubation with the affinity label reagent adenosine tetraphosphate pyridoxal (AP4-PL) at a mixing molar ratio of 5:1 AP4-PL contains structural features of the substrates pyridoxal and ATP. The substrate ATP affords substantial protection against inactivation. The extent of chemical modification by the affinity label was determined by measuring the spectroscopic properties of AP4-pyridoxyl chromophores attached to the enzyme after reduction with NaBH4. The incorporation of 2 mol of the affinity label per enzyme dimer is needed for complete inactivation of the kinase. After chymotryptic digestion of the enzyme modified with AP4-PL and reduced with tritiated NaBH4, only one radioactive peptide absorbing at 325 nm was separated by reverse-phase high performance liquid chromatography. The amino acid sequence of the radioactive peptide, elucidated by Edman degradation, revealed that a specific lysyl residue of monomeric pyridoxal kinase has reacted with the affinity label reagent. It is postulated that the modified lysyl residue is involved in direct interactions with phosphoryl groups of ATP.
authors.affiliation: Department of Biochemistry, University of Tennessee, Knoxville 37996-0840.
authors.forename: P
authors.initials: P
authors.lastname: Dominici
authors.forename: G
authors.initials: G
authors.lastname: Scholz
authors.forename: F
authors.initials: F
authors.lastname: Kwok
authors.forename: J E
authors.initials: JE
authors.lastname: Churchich
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology*; D000345:Affinity Labels / Q000494:pharmacology*; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001921:Brain / Q000201:enzymology; D007700:Kinetics; D015394:Molecular Structure; D010770:Phosphotransferases / Q000378:metabolism*; D011485:Protein Binding; D011730:Pyridoxal / Q000031:analogs & derivatives* / Q000494:pharmacology; D011731:Pyridoxal Kinase / Q000378:metabolism*; D012756:Sheep; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000227:Adenine Nucleotides; D000345:Affinity Labels; D000596:Amino Acids; C049518:adenosine tetraphosphopyridoxal; D011730:Pyridoxal; D010770:Phosphotransferases; D011731:Pyridoxal Kinase