Binding Properties of Adenosine Deaminase Interacted with Theophylline

Abstract

Adenosine deaminase (ADA) is a glycoprotein (34.5 kDa) consisting of a single polypeptide chain of 311 amino acids, 1,2) which catalyzes the irreversible hydrolytic deamination of adenosine and 2Ј-deoxyadenosine nucleosides to their respective inosine derivative nucleosides and ammonia with a rate enhancement of 2ϫ10 12 relative to the nonenzymatic reaction.3) Catalysis requires a Zn 2ϩ cofactor.4) The enzyme is widely distributed in vertebrates, invertebrates and mammals including humans. Aberrations in the expression and function of ADA have been implicated in several disease states such as severe combined immuno deficiency (SCID), which is characterized by impaired B-and T-cell-based immunity resulting from an inherited deficiency in ADA. 5,6) Higher level of ADA in the alimentarytract and decidual cells of the developing fetal-maternal interface put ADA among those enzymes performing unique roles related to grows rate of cells, embryo implantation, and other undetermined functions. 7,8) The inhibition of adenosine deaminase in brain would allow an accumulation of adenosine, which produces vasodilation, and increase of cerebral blood flow. Therefore the decrease of enzyme activity would potentiate the sedative actions of adenosine in interneuronal communication of the central nervous system. 9)ADA has a (a/b) barrel structure motif. The active site of ADA resides at the C-terminal end of the b barrel, in a deep oblong-shaped pocket. A pentacoordinated Zn 2ϩ cofactor is embedded in the deepest part of the pocket. The zinc ion is located deep within the substrate binding cleft and coordinated in a tetrahedral geometry to His 15, His 17, His 214, and Asp 295. A water molecule, which shares the ligand coordination site with Asp 295, is polarized by the metal giving rise to a hydroxylate ion that replaces the amine at the C6 position of adenosine through a stereo specific additionelimination mechanism.10) Mutation studies of amino acids in the proposed active site near the zinc binding site in the adenosine deaminase confirmed the essential role of these residues in catalysis. [11][12][13] ADA can hydrolyze the substituent in 6 position of a variety of substituted purine nucleosides. The enzyme' hydrolytic capabilities have been exploited to convert lipophilic 6-substituted purine nucleosides to products which show anti-HIV (human immunodeficiency virus) activity. 14,15) Understanding the interaction of ADA with its effectors at molecular level will be important in the development of the next generation of pharmaceutical agents that act as inhibitors, activator, or substrates. Isothermal titration calorimetry (ITC) gives valuable information about biomacromolecule-ligand interaction and enzyme inhibition. [16][17][18][19][20][21][22][23][24] Following our previous research on modified histidine residues 25) and inhibition study of ADA by inosine, 26) caffeine 27) and acetaminophen, 28) in this work we describe the binding properties of ADA interacted with theophylline studied by isothermal titration calorimetry us...

Thermodynamic Study of Myelin Basic Protein upon Interaction with [Hg2+] Using Extension Solvation Model

“…The calorimetric data analysis using Eq. (8) is a graphical fitting model, which has been extensively applied to studies on the protein inhibition 2,16,18,19 and metal binding to proteins. [30][31][32][33][34][35][36][37][38][39] Consider, a solution containing ligand and a biomacromolecule, that contains "g" sites capable of binding the ligand.…”

“…Isothermal titration calorimetry (ITC) gives invaluable information about biomacromolecule-ligand interaction, [1][2][3][4][5][6][7][8][9] protein denaturation, [10][11][12][13][14] kinetic parameters 15 and enzyme inhibition. [16][17][18][19][20] The correlation of structural and calorimetric measurements is one of the fundamental areas of advance incorporating ITC data. The number of publications on ITC has grown exponentially over the last decade, reflecting the general utility of the method.…”

Kinetic, thermodynamic and statistical studies on the inhibition of adenosine deaminase by aspirin and diclofenac

“…The heat of dilution of the drug solution was measured as described above except that the buffer solution was injected into the protein solution in the sample cell. The enthalpies of dilution for the drug and protein solutions were subtracted from the enthalpy of the ADA-aspirin interaction as previously reported [24][25][26][27][28]. The molecular weight of ADA was taken to be 34 500 [36].…”

“…The effect of inosine [24], caffeine [25], theophyline [26], acetaminophen [27] and theobromine [28] as inhibitors on ADA activity has been studied by calorimetery and spectroscopy. The enthalpy, equilibrium and inhibition constants for binding were obtained [29,30].…”

Effects of Dimaine, Diacid and Dintitro Derivatives on the Inhibition of Adenosine Deaminase; Experimental, Molecular Docking and QSAR Studies

“…Effect of inosine, 12 caffeine, 13 theophyline, 14 acetaminophen, 15 theobromine, 16 as inhibitors on ADA activity has been studied by spectroscopy and calorimetry. The enthalpy, equilibrium and inhibition constants for binding were obtained.…”