Shin Hyunshun, Cama Evis, Christianson David W
Contribution from the Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA.
J Am Chem Soc. 2004 Aug 25;126(33):10278-84. doi: 10.1021/ja047788w.
Arginase is a binuclear manganese metalloenzyme that catalyzes the hydrolysis of l-arginine to form l-ornithine and urea. Chiral L-amino acids bearing aldehyde side chains have been synthesized in which the electrophilic aldehyde C=O bond is isosteric with the C=N bond of L-arginine. This substitution is intended to facilitate nucleophilic attack by the metal-bridging hydroxide ion upon binding to the arginase active site. Syntheses of the amino acid aldehydes have been accomplished by reduction, oxidation, and Wittig-type reaction with a commercially available derivative of L-glutamic acid. Amino acid aldehydes exhibit inhibition in the micromolar range, and the X-ray crystal structure of arginase I complexed with one of these inhibitors, (S)-2-amino-7-oxoheptanoic acid, has been determined at 2.2 A resolution. In the enzyme-inhibitor complex, the inhibitor aldehyde moiety is hydrated to form the gem-diol: one hydroxyl group bridges the Mn(2+)(2) cluster and donates a hydrogen bond to D128, and the second hydroxyl group donates a hydrogen bond to E277. The binding mode of the neutral gem-diol may mimic the binding of the neutral tetrahedral intermediate and its flanking transition states in arginase catalysis.
精氨酸酶是一种双核锰金属酶，可催化L-精氨酸水解形成L-鸟氨酸和尿素。已合成带有醛侧链的手性L-氨基酸，其中亲电醛C=O键与L-精氨酸的C=N键是等电子体。这种取代旨在促进金属桥连氢氧根离子在与精氨酸酶活性位点结合时的亲核攻击。氨基酸醛的合成已通过还原、氧化以及与L-谷氨酸的市售衍生物进行维蒂希型反应来完成。氨基酸醛在微摩尔范围内表现出抑制作用，并且已在2.2埃分辨率下测定了与这些抑制剂之一（S）-2-氨基-7-氧代庚酸复合的精氨酸酶I的X射线晶体结构。在酶-抑制剂复合物中，抑制剂醛部分水合形成偕二醇：一个羟基桥连Mn(2+)(2)簇并与D128形成氢键，第二个羟基与E277形成氢键。中性偕二醇的结合模式可能模拟精氨酸酶催化中中性四面体中间体及其侧翼过渡态的结合。
