Inosine-5 -monophosphate dehydrogenase

Inosine 5 -Monophosphate Dehydrogenase. A series of 21 known inosine 5 -monophosphate dehydrogenase (IMPDH) inhibitors was used to validate a virtual screening protocol. By application of a molecular weight filter (80 < MW < 400), 3425 compounds were extracted from an in-house reagent inventory system. Docking of these compounds into a substrate-IMPDH complex 3D structure was performed with the program FlexX three... 

F. M. McMillan, M. Gaboon, A. White, L. Hedstrom, G.A. Petsko, and D. Ringe. 2000. Crystal structure at 2.4 A resolution of Borrelia burgdorferi inosine 5 -monophosphate dehydrogenase Evidence of a substrate-induced hinged-lid motion by loop 6 Biochemistry 39 4533-4542. (PubMed)... 

Verham, R., Meek, T. D., Hedstrom, L. and Wang, C. C. (1987) Purification, characterization, and kinetic analysis of inosine 5 -monophosphate dehydrogenase of Tritrichomonas foetus. Mol. Biochem. Parasitol. 24 1-12. 

Sintchak, M.D. and Nimmesgem, E. (2000) The structure of inosine 5 -monophosphate dehydrogenase and the design of novel inhibitors. Immunopharmacology 47 163-184. 

C10H13N4O9P 364.208 Inhibitor of isoforms I and II of human inosine 5 -monophosphate dehydrogenase. No phys. props, reported. 

Inosine monophosphate dehydrogenase (EVDPDH) is a key enzyme of purine nucleotide biosynthesis. Purine synthesis in lymphocytes exclusively depends on the de novo synthesis, whereas other cells can generate purines via the so-called salvage pathway. Therefore, IMPDH inhibitors preferentially suppress DNA synthesis in activated lymphocytes. 

Inosine monophosphate dehydrogenase (IMPDH) is the key enzyme of purine nucleotide biosynthesis. Proliferation of activated lymphocytes dq ends on rapid de novo production of purine nucleotides for DNA synthesis. 

Human type II inosine monophosphate dehydrogenase catalyses NAD-dependent conversion of inosine monophosphate (IMP) into xanthosine monophosphate (XMP) measurements of the primary kinetic isotope effect using [ H]IMP suggest that both substrates (IMP and NAD) can dissociate from the enzyme-substrate complex therefore, the kinetic mechanism is not ordered. NMR studies indicate hydride transfer to the B or pro-S face of the nicotinamide ring of NAD, while kinetic studies suggest... 

Mycophenolate sodium (62 Myfortic ) Mycophenolic acid (61) Fatty acid antibiotic NP Microbial Immuno- suppression Inhibits inosine monophosphate dehydrogenase (IMPDH) activity 215-217, 532-560... 

Mycophenolate sodium (62 Myfortic Norvatis, 2003) is an immunosuppressant drug used to prevent rejection in organ transplantation. It is a selective, noncompetitive, reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in the de novo pathway of guanosine nucleotide synthesis. Thus, mycophenolic acid (61), originally... 

Mycophenolate mofetil has a more specific effect on lymphocytes than on other cells. It inhibits inosine monophosphate dehydrogenase, which catalyzes purine synthesis in lymphocytes. It is used in acute tissue rejection responses. 

Mycophenolate mofetil is used together with cyclosporine and corticosteroids for the prophylaxis of acute organ rejection in patients undergoing allogeneic renal, or hepatic transplants. Compared with azathioprine it is more lymphocyte-specific and is associated with less bone marrow suppression, fewer opportunistic infections and lower incidence of acute rejection. More recently, the salt mycophenolate sodium has also been introduced. Mycophenolate mofetil is rapidly hydrolyzed to mycopheno-lic acid, its active metabolite. Mycophenolic acid is a reversible noncompetitive inhibitor of inosine monophosphate dehydrogenase, an important enzyme for the de novo synthesis of purines. As lymphocytes have little or no salvage pathway for purine... 

Mycophenolate mofetil (MMF, CellCept) is an ester prodrug of mycophenolic acid (MPA), a Penicillium-de-rived immunosuppressive agent (see Chapter 57) that blocks de novo purine synthesis by noncompetitively inhibiting the enzyme inosine monophosphate dehydrogenase. MPA preferentially suppresses the proliferation of cells, such as T and B lymphocytes, that lack the purine salvage pathway and must synthesize de novo... 

Mechanism of Action An immunologic agent that suppresses the immunologically mediated inflammatory response by inhibiting inosine monophosphate dehydrogenase, an enzyme that deprives lymphocytes of nucleotides necessary for DNA and RNA synthesis, thus inhibiting the proliferation of T and B lymphocytes. Therapeutic Effect Prevents transplant rejection. 

Unlike these nonspecific agents, mycophenolate mofetil (6.4) tends to be a lymphocyte-specific cytotoxic agent. Mycophenolate mofetil is a semisynthetic derivative of mycophe-nolic acid, isolated from the mold Penicillium glaucum. It inhibits both T and B lymphocyte action. Since it inhibits the enzyme inosine monophosphate dehydrogenase, which catalyses purine synthesis in lymphocytes, this agent has a more specific effect on lymphocytes than on other cell types. Mizoribine (6.5) is a closely related drug which inhibits nucleotide synthesis, preferentially in lymphocytes. 

Mechanism of Action Selectively inhibits inosine monophosphate dehydrogenase in the de novo pathway of purine synthesis, producing potent cytostatic effects on T and B lymphocytes... 

Mechanism of Action. Mycophenolate mofetil inhibits a specific enzyme (inosine monophosphate dehydrogenase) that is responsible for the synthesis of DNA precursors in T and B lymphocytes.39 50 Because these lymphocytes cannot synthesize adequate amounts of DNA, their ability to replicate and proliferate is impaired, thus blunting the immune response. This drug may also inhibit lymphocyte attraction and adhesion to the vascular endothelium, thereby impairing the lymphocytes ability to migrate to the site of the foreign (transplanted) tissues and to infiltrate from the bloodstream into these tissues.50... 

Selenazofurin (158), selenophenfurin (159), and dinucleosides such as 160 (Fig. 10), are potent inosine monophosphate dehydrogenase (IMPDH) inhibitors and have pronounced antitumor activity in animals and broad spectrum antiviral as well as maturation-inducing activities [262-264], The inhibitory effects of heterocyclic organoselenium compounds such as ebselen and some of its derivatives have been demonstrated on 15-LOXs [21, 265],... 

JT Beck, S Zhao, CC Wang. Cloning, sequencing, and structural analysis of the DNA encoding inosine monophosphate dehydrogenase (EC 1.1.1.205) from Tritrichomonas foetus. Exp Parasitol 78 101-112, 1994. 

Figure 4 Pathway of thiopurine metabolism. Abbreviations TPMT, thiopurine methyltransferase XO, xanthineoxidase HPRT, hypoxanthine guanine phosphori-bosyltransferase IMPDH, inosine monophosphate dehydrogenase.

In inosine monophosphate dehydrogenase, the monovalent metal ion accelerates the hydride transfer step of the reaction with apparently few other effects on the enzyme structure. Probably the monovalent cation is involved in helping position the nicotinamide cofactor. The active site and location of the potassium ion are shown in Figure 2. Mycophenolic acid in this diagram is an inhibitor that is thought to lock inosine monophosphate into the active site, as shown. Note the large distance between the inhibitor (in the active site) and the K+. 

Figure 2 The active site of inosine monophosphate dehydrogenase, drawn from PDB file IJRl. This shows the inhibitor mycophenolic acid at the active site, stacking against PLP. The K+ site is distant from the active site...

G. D. Markham, Monovalent Cation Activation of IMP Dehydrogenase, Inosine Monophosphate Dehydrogenase A Major Therapeutic Target , K. W. Pankiewicz and B. M. Goldstein eds., ACS Symposium, series 839, Washington, DC, 2003, p. 169. 

Base-induced (KH or /-BuOK) cyclizations of o-alkynylanilines were utilized to prepare 2-substituted indoles and poly-substituted indoles. For example, treatment of alkynes 86 with KH gave the corresponding indoles 87 <03T1571>. Similar base-mediated cyclizations and related indole syntheses were utilized to prepare indole inhibitors of 5 -inosine monophosphate dehydrogenase <03BMCL1273>. Moreover, base-induced cyclizations of arylacetonitriles with oxalic acid bis(imidoyl)chlorides provide a route to 2-alkylidene-3-iminoindoles <03CEJ3951>. 

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