Reactivity of the sulfhydryl groups of muscle phosphofructokinase.
Reactivity of the sulfhydryl groups of muscle phosphofructokinase.
复制标题
肌肉磷酸果糖激酶的巯基的反应性。
DOI：
10.1021/bi00847a022
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发表时间：
1968
期刊：
影响因子：
2.9
通讯作者：
P. Forest
中科院分区：
文献类型：
--
作者：
R. G. Kemp;P. Forest
Robert G.肯普和保罗B。森林摘要：兔骨骼肌磷酸果糖激酶每90，000 g酶含有16.9±0.3个半胱氨酰残基。根据它们对5，5 '-二硫代双（2-硝基苯甲酸）的反应性，这些半胱氨酰残基可分为五类。一个单一的极端反应性SH基团表现出一个表观的二级速率常数，是2 × 104倍高于变性磷酸果糖激酶与二硫化物化合物的反应速率。第二类SH基团由两个半胱氨酰残基组成，其反应性稍低，并且被腺嘌呤核苷酸或果糖6-磷酸保护而不反应。这两个巯基与5，5 ′-二硫代双（2-硝基苯甲酸）反应，酶活损失90%以上。第三类由一个SH基团组成，其反应速率约为第二类的0.4。当反应介质的pH值增加到9时，约有5个SH基团可用于与5，5 ′-二硫代双（2-硝基苯甲酸）的快速反应。其中两个巯基被1，6-二磷酸果糖保护而不能与5，5 '-二硫代双（2-硝基苯甲酸）反应，其余的巯基与5，5'-二硫代双（2-硝基苯甲酸）反应非常缓慢，只有在酶的三级结构被破坏后才能快速反应。本文报道了一种用于制备结晶型兔骨骼肌磷酸果糖激酶的酶原。
Robert G. Kemp and Paul B. Forest abstract: Rabbit skeletal muscle phosphofructokinase contains 16.9±0.3 cysteinyl residues per 90,000 g of enzyme. On the basis of their reactivity toward 5, 5'-dithiobis (2-nitrobenzoic acid), these cysteinyl residues may be classified into fivegroups. A single exceedingly reactive SH group exhibits an apparent second-order rate constant that is 2 X 104 times higher than the rate of the reaction of denatured phosphofructokinase with the disulfide compound. The second class of SH groups consists of two cysteinyl residues that are somewhat less reactive and are protected from reaction by either ade-nine nucleotides or fructose 6-phosphate. The reaction of these two SH groups with 5, 5'-dithiobis (2-nitro-benzoic acid) results in the loss of more than 90% of the enzyme activity. The third class consists of one SH group that reacts at about 0.4 of the rate of the second class. Approximately five SH groupsbecome available for rapidreaction with 5, 5'-dithiobis (2-nitrobenzoic acid) as the pH of the reaction medium is increased to 9. Two of these SH groups are protected from reaction with 5, 5'-dithiobis (2-nitrobenzoic acid) by fructose 1, 6-diphosphate.The remaining SH groups react very slowly with 5, 5'-dithiobis (2-nitrobenzoic acid) and can be made available for rapidreaction only if the tertiary structure of the enzyme is destroyed. A simplifiedpro-cedure for the preparation of crystalline rabbit skeletal muscle phosphofructokinase is described.