AMINO-ACID EFFECTOR BINDING TO RABBIT MUSCLE PYRUVATE-KINASE
AMINO-ACID EFFECTOR BINDING TO RABBIT MUSCLE PYRUVATE-KINASE
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DOI：
10.1016/0003-9861(73)90455-4
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发表时间：
1973-01-01
影响因子：
3.9
通讯作者：
PRICE, NC
中科院分区：
文献类型：
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作者：
KAYNE, FJ;PRICE, NC
兔肌肉丙酮酸激酶的变构抑制剂L-苯丙氨酸显示以每摩尔四聚体4摩尔效应物的比率与四聚体酶结合。这种结合在不存在二价阳离子活化剂的情况下是轻微合作的，但当在2.5 mmMg 2+或Mn 2+的存在下测量时，协同性强烈增加。在这些条件下，效应子亲和力有所降低。已知l-丙氨酸拮抗所有测定的苯丙氨酸效应，并且在此显示也结合蛋白质上的4个位点。的结合是非合作的，很少受到二价活化阳离子的存在下。与苯丙氨酸和丙氨酸的竞争实验表明竞争相同的网站。在β-烯醇式丙酮酸和Mg ~（2+）浓度低于100 μ m时的底物动力学测定表明，苯丙氨酸浓度在100 μm左右时，对酶有相当大的抑制作用，接近血清游离氨基酸水平。接近苯丙氨酸抑制速度的半衰期小于1秒。
l-Phenylalanine, an allosteric inhibitor of rabbit muscle pyruvate kinase, is shown to bind to the tetrameric enzyme in a ratio of 4 moles effector per mole of tetramer. This binding is slightly cooperative in the absence of divalent cation activators, but the cooperativity is strongly increased when measured in the presence of 2.5 mmMg2+or Mn2+. The effector affinity is somewhat decreased under these conditions.l-Alanine was known to antagonize all measured phenylalanine effects and is shown here to also bind to 4 sites on the protein. The binding is noncooperative and little affected by the presence of the divalent activating cations. Competition experiments with phenylalanine and alanine suggest competition for the same site. Substrate kinetic measurements atP-enolpyruvate and Mg2+concentrations under 100 μmshow considerable inhibition of the enzyme at phenylalanine concentrations around 100 μm, near the serum levels of the free amino acid. The approach to the phenylalanine-inhibited velocity occurs with half-times less than 1 sec.