Inosine-5 -monophosphate formation

Fig. 8. The efiect of P5C on inosine monophosphate formation. Erythrocytes were incubated with 25 /iM [ C]hypoxanthine for 1 hour and nucleotides were separated using high-pressure liquid chromatography. The concentration of P5C was 0.5 mM. IMP pools in P5C-treated ( ) and control (O) cells as well as the incorporation of [ C]hypoxanthine into IMP in P5C-treated (A) and control (A) cells are shown. Taken from ref. (118).

One of the steps in the biosynthesis of a nucleotide called inosine monophosphate is the formation of aminoimidazole ribonucleotide from formyjglycin-amidine ribonucleotide. Propose a mechanism. 

All biosynthetic pathways are under regulatory control by key allosteric enzymes that are influenced by the end products of the pathways. For example, the first step in the pathway for purine biosynthesis is inhibited in a concerted fashion by nucleotides of either adenine or guanine. In addition, the nucleoside monophosphate of each of these bases inhibits its own formation from inosine monophosphate (IMP). On the other hand, adenine nucleotides stimulate the conversion of IMP into GMP, and GTP is needed for AMP formation. 

Other workers have also investigated the binding mode of inosine, 1-methylinosine, and 5 -inosine monophosphate towards cis-[Pt(NH3)2] and [Pt(en)] " as a function of pH using H n.m.r. and Raman spectroscopy.Stable complexes are formed over a wide range of pH mono- and bis-complexes, co-ordinated at N(7), are formed with inosine and 1-methylinosine at pH <6, while for pH >6 protons are dissociated from N(l) and co-ordination occurs at both N(7) and N(l) with formation of polynuclear complexes indicated from the spectroscopic results. 

There are no major apparent controls for PRNH2 to inosine monophosphate. For GMP or AMP, each of the purine nucleotides inhibits the pathway for the formation of more of the same nucleotide. For example, GMP will inhibit... 

Mycophenolate mofetil is a prodrug that is rapidly hydrolyzed to MPA, a selective, noncompetitive, and reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), an important enzyme in the de novo pathway of guanine nucleotide synthesis. B and T lymphocytes are highly dependent on this pathway for cell proliferation, while other cell types can use salvage pathways MPA therefore selectively inhibits lymphocyte proliferation and functions, including antibody formation, cellular adhesion, and migration. 

Nucleotide biosynthesis, like nucleotide catabolism, is relatively complex. Thus, we ll again look at only one example, adenosine monophosphate. Purine nucleotides are formed by initial attachment of an -NH2 group to ribose, followed by multistep buildup of the heterocyclic base. The attachment of -NH2 takes place by a nucleophilic suhstitution reaction of ammonia with 5-phosphoribosyl a-diphosphate to give /3-5-phosphorihosylamine and probably involves an SNl-like loss of diphosphate ion with formation of an 0x0-nium-ion intermediate. Although we ll not cover the details of its formation, inosine monophosphate (IMP) is the first fully formed purine ribonucleotide, with adenosine monophosphate (AMP) derived fi-om it. 

Write the mechanism of the formation of adenylosuccinate from inosine monophosphate, the second step in adenosine biosynthesis (Figure 24.12). 

Inosine monophosphate and GMP are synthesized in the human body and play diverse roles in cellular metabolism [3]. Dietary nucleotides are energetically useful to fulfill the liver s need for nucleotides [4], although people with high levels of uric acid (UA) in their blood and urine must avoid foods with these compounds, because degradation of purine nucleotides leads to the formation of UA [3]. In addition, these flavor enhancers are added by food manufacturers to improve the taste of food. Therefore, monitoring these compounds in foods or food seasonings is very important in food-quality or foodprocessing control. 

In a similar way, enzymes from Azotobacter vinelandii catalyze the transfer of phosphate from adenosine 5-triphosphoric acid and inosine 5-tri-phosphoric acid to the 2-deoxypentonucleoside monophosphates, with the formation of the pyrophosphates and triphosphates. ... 

Pierre, K.J. LePage, G.A. Formation of inosine-5-monophosphate by a kinase in cell-free extracts of Ehrlich ascites cells in vitro. Proc. Soc. Exp. Biol. Med., 127, 432-440 (1968)... 

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