Phosphoenzymes formed from Mg.ATP and Ca.ATP during pre-steady state kinetics of sarcoplasmic reticulum ATPase.
作者： S Orlowski , S Lund , J Møller , P Champeil
DOI: 10.1016/S0021-9258(19)77874-0
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摘要: Abstract We have investigated here the pre-steady state kinetics of sarcoplasmic reticulum ATPase incubated under conditions where significant amounts Mg.ATP and Ca.ATP coexist, both them being substrates for ATPase. confirmed that these two are independently hydrolyzed by ATPase, which thus apparently catalyzes Pi production simultaneous separate pathways. External calcium (or Ca2+/Mg2+ ratio) determines extent to Ca2+ or Mg2+ is bound at phosphorylation site, while internal controls rate processing slow, calcium-containing fast, magnesium-containing phosphoenzyme. Time-dependent binding catalytic site correlated with observed burst liberation, therefore results from reequilibration during magnesium- phosphoenzyme pools. Independently direct exchange metal ADP produced hydrolysis reaction contributes pools through reversal ATP-ADP pathway.
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