title: Modification of gastric (H+ + K+)-ATPase with pyridoxal 5'-phosphate.
abstract: Pig gastric membrane vesicles enriched in (H+ + K+)-ATPase were covalently modified with pyridoxal 5'-phosphate (PLP). The modification resulted in inhibition of K+-dependent ATP hydrolysis, formation of phosphoenzyme and ATP-driven H+-uptake catalyzed by (H+ + K+)-ATPase. ATP, ADP, and adenyl-5'-yl imidodiphosphate were protective ligands, whereas Mg2+ and K+ were not. Specific PLP-binding of about 4.5 nmol/mg membrane protein was necessary for complete inhibition of the enzyme activity, indicating that the stoichiometry of PLP-binding to the enzyme was about 1:1. Limited proteolysis of the enzyme modified with [3H]PLP by trypsin suggests that PLP specifically modifies the lysine residue located in the 16-kDa fragment of the enzyme cleaved by trypsin. These results suggested that PLP binds to a specific lysine residue in the nucleotide-binding site or a region in its vicinity and inhibits the substrate binding or phosphorylation step of (H+ + K+)-ATPase.
authors.affiliation: Department of Organic Chemistry and Biochemistry, Osaka University, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Maeda
authors.forename: M
authors.initials: M
authors.lastname: Tagaya
authors.forename: M
authors.initials: M
authors.lastname: Futai
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D005753:Gastric Mucosa / Q000201:enzymology*; D017506:H(+)-K(+)-Exchanging ATPase; D006868:Hydrolysis; D007700:Kinetics; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D011485:Protein Binding; D011732:Pyridoxal Phosphate / Q000494:pharmacology*; D012265:Ribonucleotides / Q000494:pharmacology; D013552:Swine; D014357:Trypsin
chemical_list: D010446:Peptide Fragments; D012265:Ribonucleotides; D011732:Pyridoxal Phosphate; D014357:Trypsin; D000251:Adenosine Triphosphatases; D017506:H(+)-K(+)-Exchanging ATPase