Interactions of phospho- and dephosphosuccinyl coenzyme A synthetase with manganous ion and substrates. Studies of manganese complexes by NMR relaxation rates of water protons.

摘要: Abstract The interactions of substrates with succinyl-CoA synthetase were investigated by measuring the enhancement longitudinal water proton relaxation rate (PRR) due to Mn(II) enzyme substrate complexes. binding was EPR. effects phosphorylating on its and also examined. binds weakly dephosphosuccinyl-CoA (E) at approximately four sites a KD value 0.14 mM, PRR complex, epsilonb, 24.3 MHZ 25 degree is 18.8. phosphoenzyme (E-P) more strongly 0.74 only small change in epsilonb 18.1. Mm ADP E one or two K2 = 0.5 muM, values epsilont for ternary E-Mn-ADP complex 17.0. Free about 126 times than does Mn-ADP. titrations indicated that (E-P)-Mn-ADP complexes are same. Mn-ATP very not all (E-P)-Mn.Formation CoA E-Mn (E-P)-Mn could be followed but significant increases enhancement. No succinate detected since addition had no effect However, large decrease enhancement, least 2-fold, observed upon both CoA. An increase produced interaction complex. Upper limits dissociation constants from quaternary E-Mn-ADP-succinate-CoA E-Mn-ADP-succinyl-CoA 390 560 respectively. epsilon quinary 6.4 3.1, successive occupation produces alterations molecular dynamics conformation active site (or both), which accompanied progressive decreases epsilon. Thus, physical parameter used these studies relects previously catalytic properties system inasmuch as function potentiated binding, avtivity partial reactions maximized successively occupied.