Innocenti Alessio, Firnges Michael A, Antel Jochen, Wurl Michael, Scozzafava Andrea, Supuran Claudiu T
Università degli Studi di Firenze, Laboratorio di Chimica Bioinorganica, Rm. 188, Via della Lastruccia 3, I-50019 Sesto Fiorentino (Firenze), Italy.
Bioorg Med Chem Lett. 2004 Dec 6;14(23):5769-73. doi: 10.1016/j.bmcl.2004.09.063.
The membrane-associated human isozyme of carbonic anhydrase, hCA IV, has been investigated for its interaction with anion inhibitors, for the CO(2) hydration reaction catalyzed by this enzyme. Surprisingly, halides were observed to act as potent hCA IV inhibitors, with inhibition constants in the range of 70-90 microM, although most of these ions, and especially fluoride, the best hCA IV inhibitor among the halides, are weak inhibitors of other isozymes, such as hCA I, II and V. The metal poisons cyanate, cyanide and hydrogen sulfide were weaker hCA IV inhibitors (K(i)'s in the range of 0.6-3.9 mM), whereas thiocyanate, azide, nitrate and nitrite showed even weaker inhibitory properties (K(i)'s in the range of 30.8-65.1 mM). Sulfate was a good hCA IV inhibitor (K(i) of 9 mM), although it is a much weaker inhibitor of isozymes I, II, V and IX. Excellent hCA IV inhibitory properties showed sulfamic acid, sulfamide, phenylboronic acid and phenylarsonic acid, with K(i)'s in the range of 0.87-0.93 microM, whereas their affinities for the other investigated isozymes were in the millimolar range. The interaction of some anions with the mitochondrial isozyme hCA V has also been investigated for the first time here. It has been observed that among all these isozymes, hCA V has the lowest affinity for bicarbonate and carbonate (K(i)'s in the range of 82-95 mM), which may represent an evolutionary adaptation of this isozyme to the rather alkaline environment (pH 8.5) within the mitochondria, where hCA V plays important functions in some biosynthetic reactions involving carboxylating enzymes (pyruvate carboxylase and acetyl coenzyme A carboxylase). There are important differences of affinity for anions between the two membrane-associated isozymes, hCA IV and hCA IX.
人们对碳酸酐酶的膜相关人类同工酶hCA IV与阴离子抑制剂的相互作用以及该酶催化的CO₂水合反应进行了研究。令人惊讶的是，卤化物被发现是hCA IV的有效抑制剂，其抑制常数在70 - 90微摩尔范围内，尽管这些离子中的大多数，尤其是氟化物（卤化物中最好的hCA IV抑制剂），对其他同工酶如hCA I、II和V是弱抑制剂。金属毒物氰酸盐、氰化物和硫化氢是较弱的hCA IV抑制剂（抑制常数在0.6 - 3.9毫摩尔范围内），而硫氰酸盐、叠氮化物、硝酸盐和亚硝酸盐的抑制特性甚至更弱（抑制常数在30.8 - 65.1毫摩尔范围内）。硫酸盐是一种良好的hCA IV抑制剂（抑制常数为9毫摩尔），尽管它对同工酶I、II、V和IX的抑制作用要弱得多。氨基磺酸、磺胺、苯硼酸和苯胂酸表现出优异的hCA IV抑制特性，抑制常数在0.87 - 0.93微摩尔范围内，而它们对其他所研究同工酶的亲和力在毫摩尔范围内。本文还首次研究了一些阴离子与线粒体同工酶hCA V的相互作用。据观察，在所有这些同工酶中，hCA V对碳酸氢盐和碳酸盐的亲和力最低（抑制常数在82 - 95毫摩尔范围内），这可能代表了该同工酶对线粒体中相当碱性的环境（pH 8.5）的一种进化适应，在该环境中hCA V在一些涉及羧化酶（丙酮酸羧化酶和乙酰辅酶A羧化酶）的生物合成反应中发挥重要作用。两种膜相关同工酶hCA IV和hCA IX对阴离子的亲和力存在重要差异。
