Nucleotide utilization

Hampton, A., Sasaki, T., and Paul, B., Synthesis of 6 -cyano-6 -deoxyhomoadenosine-6 -phosphonic acid and its phosphoryl and pyrophosphoryl anhydrides and studies of their interactions with adenine nucleotide utilizing enzymes, J. Am. Chem. Soc., 95, 4404, 1973. 

Zhang, J., and Xu, X., Total synthesis of 6-ep/-sarsolilide A, Tetrahedron Lett., 41, 941, 2000. Boehm, H.M.. I landa, S., Pattenden, G., Roberts. L.. Blake, A.J., and Li, W.-S., Cascade radical cyclizations leading lo steroid ring constructions. Regio- and stereo-chemical studies using ester- and fluoroalkene substituted polyene acyl radical intermediates.,/. Chem. Soc., Perkin Trans. 1, 3522, 2000. Hampton, A.. Sasaki, T, and Paul, B., Synthesis of 6 -cyano-6 -deoxyhomoadenosine-6 -phosphonic acid and its phosphoryl and pyrophosphoryl anhydrides and studies of their interactions with adenine nucleotide utilizing enzymes, J. Am. Chem. Soc.. 95. 4404, 1973. 

The enzyme from E. coli utilizes ATP and ADP as substrates in place of the guanine nucleotides utilized by the mammalian enzymes. The mechanism of this reaction is reviewed in Volume X of this series (87). It is an interesting mechanism in that it involves an intermediate phosphoenzyme, with the phosphoryl group bonded to a histidine imidazole ring. The chemical reaction pathway consists of reactions (27a)-(27c), in which succinyl phosphate is an enzyme-bound intermediate. 

The title compound (I) can be viewed as an enzyme affinity label produced by attachment of a relatively small leaving group (chlorine) to a hydrophilic substrate (inosine 5 -phosphate) in the expectation that the enzymic substrate binding sites will contain a preponderance of hydrophilic and hence potentially derivatizable amino acid residues. Evidence indicates that (I) forms covalent bonds at the nucleotide binding sites of two of four purine nucleotide utilizing enzymes which were examined. 

ANTTBIOTTCS - NUCLEOSIDES AND NUCLEOTIDES] (Vol 3) PURPA. See Public Utility Regulatory Policy Act. 

The deterrnination of the presence of reverse transcriptase in vims-infected cells can be done using labeled nucleotide triphosphates. Reverse transcriptase is an enzyme capable of synthesizing DNA from RNA and it is thought to play an important role in vims-mediated cell modification. This enzyme is also a marker enzyme for HIV, the vims impHcated in causing acquired immunodeficiency syndrome (AIDS). The procedure utilizes radiolabeled nucleotides with nonlabeled substrates to synthesize tagged DNA. The degree of radioactive incorporation reflects the reverse transcriptase activity. 

This enzyme interconverts ribulose-5-P and ribose-5-P via an enediol intermediate (Figure 23.30). The reaction (and mechanism) is quite similar to the phosphoglucoisomerase reaction of glycolysis, which interconverts glucose-6-P and fructose-6-P. The ribose-5-P produced in this reaction is utilized in the biosynthesis of coenzymes (including N/ DH, N/ DPH, F/ D, and Big), nucleotides, and nucleic acids (DNA and RNA). The net reaction for the first four steps of the pentose phosphate pathway is... 

The utility of the Zincke reaction has been extended to the preparation of various NAD and NADH analogs. Holy and co-workers synthesized a series of NAD analogs containing nucleotide bases as a means to study through-space interaction between the pyridinium and base portions. Nicotinamide-derived Zincke salt 8 was used to link with various adenine derivatives via tethers that contained hydroxyl (105 —> 106, Scheme 8.4.35), phosphonate (107—>108, Scheme 8.4.36), and carboxylate "... 

Monomeric actin binds ATP very tightly with an association constant Ka of 1 O M in low ionic strength buffers in the presence of Ca ions. A polymerization cycle involves addition of the ATP-monomer to the polymer end, hydrolysis of ATP on the incorporated subunit, liberation of Pi in solution, and dissociation of the ADP-monomer. Exchange of ATP for bound ADP occurs on the monomer only, and precedes its involvement in another polymerization cycle. Therefore, monomer-polymer exchange reactions are linked to the expenditure of energy exactly one mol of ATP per mol of actin is incorporated into actin filaments. As a result, up to 40% of the ATP consumed in motile cells is used to maintain the dynamic state of actin. Thus, it is important to understand how the free energy of nucleotide hydrolysis is utilized in cytoskeleton assembly. 

Since biosynthesis of IMP consumes glycine, glutamine, tetrahydrofolate derivatives, aspartate, and ATP, it is advantageous to regulate purine biosynthesis. The major determinant of the rate of de novo purine nucleotide biosynthesis is the concentration of PRPP, whose pool size depends on its rates of synthesis, utilization, and degradation. The rate of PRPP synthesis depends on the availabihty of ribose 5-phosphate and on the activity of PRPP synthase, an enzyme sensitive to feedback inhibition by AMP, ADP, GMP, and GDP. 

Liver, the major site of purine nucleotide biosynthesis, provides purines and purine nucleosides for salvage and utilization by tissues incapable of their biosynthesis. For example, human brain has a low level of PRPP amidotransferase (reaction 2, Figure 34-2) and hence depends in part on exogenous purines. Erythrocytes and polymorphonuclear leukocytes cannot synthesize 5-phosphoribosylamine (strucmre III, Figure 34-2)... 

Silver ions will oxidatively desulphurize nucleoside and other phos-phorothioates to generate a phosphorylating agent. This reaction has been utilized for the preparation of nucleotide coenzymes and has the advantage that it can be carried out on a large scale without the formation of contaminating symmetrical pyrophosphates. 

The potential clinical utility of the bDNA assay in AIDS patients was demonstrated by monitoring CMV DNA levels in the blood of a patient undergoing gan-cilovir therapy (Chemoff et al 1997), in semen specimens from patients being treated with the antiviral nucleotide analogue cidofovir (Lalezari et al 1995), and in cerebrospinal fluid from patients with CMV neurologic infections (Flood et ai, 1997). These studies demonstrate that bDNA can be used to measure CMV DNA in various clinical specimens. To date, no comparisons of bDNA with other strategies for detection of CMV DNA in clinical specimens have been published. 

---