In vitro activity: Tenatoprazole labeled only the gastric H+,K+-ATPase alpha-subunit as has been found for other PPIs, approximately 2.6 nmol/mg of tenatoprazole is bound to the H+,K+-ATPase. The two enantiomers (R)- or (S)-tenatoprazole give the same stoichiometry of binding with 88% inhibition. Tenatoprazole labels only the peptide containing fifth and sixth transmembrane segments, these contain two cysteines, cysteine 813 in the luminal vestibule and cysteine 822 in the sixth transmembrane domain.

Kinase Assay: The enzyme suspension (20 mg/mL) is incubated at 37°C in a buffer composed of 5 mM Pipes/Tris (pH 6.95), 2 mM MgCl2, 150 mM KCl, 3 mg/mL of valinomycin, 1 mM acridine orange, in the presence of 0.1 mM glutathione, in a SPEX spectrofluorometer for 5 min. Inhibitor (20 mM), omeprazole or tenatoprazole, is added and fluorescence is measured by excitation at 490 nm and emission at 530 nm. After 60 s, ATP (2 mM) is added to initiate acridine orange uptake as a measure of intra-vesicular acidification.

Biochem Pharmacol. 2006 Mar 14;71(6):837-49.