用磷酸吡哆醛修饰（钠钾）-ATP酶对其钠型和钾型之间平衡的影响。

Effect on the equilibrium between the Na+-form and the K+-form of the (Na+ + K+)-ATPase of modification of the enzyme with pyridoxal 5-phosphate.

作者信息

Skou J C

出版信息

Biochim Biophys Acta. 1984 Aug 28;789(1):44-50. doi: 10.1016/0167-4838(84)90058-x.

Abstract

An increase in pH shifts the equilibrium between the K+-form and the Na+-form of the (Na+ + K+)-ATPase towards the Na+-form. pK for the proton effect on the equilibrium is decreased by modification of the enzyme with pyridoxal 5-phosphate. The reactivity of the enzyme towards pyridoxal 5-phosphate is increased by an increase in pH. Modification by pyridoxal 5-phosphate of epsilon-amino groups on lysine, which has a pK of about 8 with the enzyme in the K+-form and of about 7.4 in the Na+-form, shifts the equilibrium between E1Na+ and E2 towards E2, and the equilibrium between E2(K+occ) and E2 towards E2, but has no effect on the overall equilibrium between E1Na+ and E2(K+occ). An additional modification of epsilon-amino groups on lysine, which has a pK of 9.5-10 with the enzyme in the K+-form and of about 7.7 with the enzyme in the Na+-form, shifts the equilibrium between E2(K+occ) and E1Na+ towards E1Na+; this is due to a shift in the equilibrium between E2(K+occ) and E2 towards E2, but with no effect on the equilibrium between E1Na+ and E2. The results show that the transition from the K+-form to the Na+-form decreases the pK of lysine epsilon-amino groups on the enzyme, and that the protonation of these groups influences the equilibrium between the two conformations.

摘要

pH值升高会使（Na⁺+K⁺）-ATP酶的K⁺型和Na⁺型之间的平衡向Na⁺型移动。质子对该平衡的效应的pK值会因用磷酸吡哆醛修饰酶而降低。酶对磷酸吡哆醛的反应活性会因pH值升高而增加。磷酸吡哆醛对赖氨酸上ε-氨基的修饰，在K⁺型酶中其pK约为8，在Na⁺型酶中约为7.4，会使E1Na⁺和E2之间的平衡向E2移动，以及使E2（K⁺占据）和E2之间的平衡向E2移动，但对E1Na⁺和E2（K⁺占据）之间的总体平衡没有影响。对赖氨酸上ε-氨基的进一步修饰，在K⁺型酶中其pK为9.5 - 10，在Na⁺型酶中约为7.7，会使E2（K⁺占据）和E1Na⁺之间的平衡向E1Na⁺移动；这是由于E2（K⁺占据）和E2之间的平衡向E2移动，但对E1Na⁺和E2之间的平衡没有影响。结果表明，从K⁺型向Na⁺型的转变会降低酶上赖氨酸ε-氨基的pK值，并且这些基团的质子化会影响两种构象之间的平衡。