Schuster S M, Ebel R E, Lardy H A
J Biol Chem. 1975 Oct 10;250(19):7848-53.
Mitochondrial ATPases from rat liver and beef heart were used to study the effects of guanylylimidodiphosphate (GMP-P(NH)P) and adenylylimidodiphosphate (AMP-P(NH)P) on the kinetics of MgATP, MgITP, and MgGTP hydrolysis. AMP-P(NH)P was a noncompetitive inhibitor of hydrolysis of all substrates with the rat liver enzyme, whether activating anions were present or not. Also with the liver enzyme, AMP-P(NH)P caused only MgATP hydrolysis to appear to have positive cooperativity. With the beef heart enzyme, AMP-P(NH)P was a competitive inhibitor of ATPase activity and caused positive cooperativity; it gave noncompetitive patterns with GTP or ITP as substrates. In both enzyme systems, GMP-P(NH)P gave complex inhibition patterns with MgATP as the substrate, but was a competitive inhibitor of MgITP and MgGTP hydrolysis. These results are interpreted as indicating the existence of two types of nucleotide binding sites, with varying degrees of specificity and interaction on the ATPase molecules from both sources. It is postulated that MgATP and AMP-P(NH)P bind to regulatory site while MgATP, MgGTP, Mgitp, and GMP-P(NH)P bind to the catalytic site.
来自大鼠肝脏和牛心脏的线粒体ATP酶被用于研究鸟苷酰亚胺二磷酸（GMP-P(NH)P）和腺苷酰亚胺二磷酸（AMP-P(NH)P）对MgATP、MgITP和MgGTP水解动力学的影响。对于大鼠肝脏的酶，无论是否存在激活阴离子，AMP-P(NH)P都是所有底物水解的非竞争性抑制剂。同样对于肝脏的酶，AMP-P(NH)P仅使MgATP水解表现出正协同性。对于牛心脏的酶，AMP-P(NH)P是ATP酶活性的竞争性抑制剂并导致正协同性；以GTP或ITP为底物时呈现非竞争性模式。在这两种酶系统中，以MgATP为底物时，GMP-P(NH)P呈现复杂的抑制模式，但它是MgITP和MgGTP水解的竞争性抑制剂。这些结果被解释为表明存在两种类型的核苷酸结合位点，在来自这两种来源的ATP酶分子上具有不同程度的特异性和相互作用。据推测，MgATP和AMP-P(NH)P结合到调节位点，而MgATP、MgGTP、MgITP和GMP-P(NH)P结合到催化位点。
