Kobayashi M, Soman G, Graves D J
J Biol Chem. 1982 Dec 10;257(23):14041-7.
Characteristics of the activator sites of liver and muscle phosphorylase b were probed by using AMP and AMP analogs in kinetic studies, by quantitative affinity chromatography, and by reaction with an affinity-labeling reagent. Activation of liver phosphorylase b by N6-(6-aminohexyl)AMP in comparison with AMP and other analogs is explained by preferential binding to the activator site. The KM value for glucose-1-P of liver phosphorylase b activated with N6-(6-aminohexyl)AMP is considerably higher than that of muscle phosphorylase b. Affinity chromatography utilizing AMP-Sepharose suggests that the activator site is less well formed in liver phosphorylase than in muscle phosphorylase. Reaction with 8-[m-(m-fluorosulfonylbenzamido)benzylthio]adenine activates liver phosphorylase b and is consistent with the reaction at the activator site. The results suggest that part of the reason that liver phosphorylase b is not activated by AMP and AMP analogs is due to a poor coupling between the activator and active sites. Lack of good activation by AMP also can be explained by binding at the inhibitor site.
通过动力学研究中使用AMP及其类似物、定量亲和色谱法以及与亲和标记试剂反应，对肝脏和肌肉磷酸化酶b的激活位点特性进行了探究。与AMP和其他类似物相比，N6-(6-氨基己基)AMP对肝脏磷酸化酶b的激活作用可通过其与激活位点的优先结合来解释。用N6-(6-氨基己基)AMP激活的肝脏磷酸化酶b对葡萄糖-1-磷酸的KM值明显高于肌肉磷酸化酶b。利用AMP-琼脂糖进行的亲和色谱表明，肝脏磷酸化酶中激活位点的形成不如肌肉磷酸化酶中那样完善。与8-[间-(间-氟磺酰苯甲酰胺基)苄硫基]腺嘌呤反应可激活肝脏磷酸化酶b，这与在激活位点的反应一致。结果表明，肝脏磷酸化酶b未被AMP及其类似物激活的部分原因是激活位点与活性位点之间的偶联不佳。AMP缺乏良好的激活作用也可通过其在抑制剂位点的结合来解释。
