Premium
Pre‐steady state kinetics of ATP hydrolysis by Na,K‐ATPase
Author(s) -
Manzoor Nikhat,
Haque Mohammad M.,
Khan Luqman A.
Publication year - 2009
Publication title -
cell biochemistry and function
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 61
eISSN - 1099-0844
pISSN - 0263-6484
DOI - 10.1002/cbf.1545
Subject(s) - chemistry , hydrolysis , steady state (chemistry) , absorption (acoustics) , kinetics , atp hydrolysis , alkalinity , atpase , ion , analytical chemistry (journal) , phase (matter) , inorganic chemistry , chromatography , enzyme , biochemistry , organic chemistry , materials science , physics , quantum mechanics , composite material
Fast reaction kinetics of ATP hydrolysis by Na,K‐ATPase has been investigated by following absorption pattern of pH sensitive dye in stopped flow spectrophotometer. Distinct pre‐steady state phase signal could be recorded with an initial decrease in acidity followed by increase in acidity. Average half time for H + absorption and peak alkalinity was, respectively, 30 ms and 60 ms. Under optimal Na + (120 mM) and K + (30 mM) concentrations, magnitude of both H + absorption and H + release are found to be about 1.0 H + /ATPase molecule. H + absorption and release decreased with decrease in Na + concentration, H + release was more affected. Both H + absorption and H + release are found to be independent of K + concentration in the pre‐steady state phase. No H + absorption or release was observed following mixing of either ADP, Na + or K + alone with ATPase. Effect of delayed mixing of Na + or K + on two phases of pre‐steady state cycle indicates that ATP hydrolytic cycle starts without K + ions if optimal Na + is present. ATP hydrolytic cycle does not start in the absence of Na + ions. Results obtained have been interpreted in terms of an extended kinetic scheme for Na,K‐ATPase. Copyright © 2009 John Wiley & Sons, Ltd.