Nucleotide Variants of the BH4 Biosynthesis Pathway …

Scheme of the purine metabolismpathways, showing the position of IMPDH2, APRT and PNP in purinenucleotide biosynthesis, adopted from a previous study (35). The de novo synthesis ofpurine nucleotides begins with the phosphorylation ofribose-5-phosphate to form PRPP. In a number of reactions, PRPPcreates the first fully formed nucleotide, IMP. IMP is converted byIMPDH2 to GMP. PNP catalyzes the reversible cleavage of purinenucleosides, releasing purine nucleobases (adenine, hypoxanthine,xanthine and guanine). In the salvage pathway the free nucleobasescan be reconverted back to nucleoside-5′-monophosphates in areaction with activated sugar (PRPP) catalyzed by APRT. IMPDH2,inosine-5′-monophosphate dehydrogenase 2; APRT, adeninephosphoribosyltransferase; PNP, purine nucleoside phosphorylase;PRPP, 5-phosphoribosyl-1-pyrophosphate; IMP,inosine-5′-monophosphate; GMP, guanosine-5′-monophosphate; dADP,deoxyadenosine diphosphate; ADP, adenosine diphosphate; GDP,guanosine diphosphate; dGDP, deoxyguanosine diphosphate; AMP,adenosine monophosphate; XMP, xanthosine monophosphate.

Nucleotide Metabolism: Nucleic Acid Synthesis

of the DHODH in the de novo pyrimidine nucleotide biosynthesis pathway.

KEGG PATHWAY: Metabolic pathways - Reference pathway

We examine here the biosyntheticpathways of purine and pyrimidine nucleotides and their regulation, theformation of the deoxynucleotides, and the degradation of purines andpyrimidines to uric acid and urea.

The L-Arginine-Nitric Oxide Pathway — NEJM

My salvage pathway of purine nucleotide biosynthesis include me at my computer to guarantee a happy enough as on my assignment while enjoying one language from part of it.

Activation of the de Novo Pathway for Pyridine Nucleotide Biosynthesis Prior to Ricinine Biosynthesis in ..
Helicobacter pylori Relies Primarily on the Purine Salvage Pathway for Purine Nucleotide Biosynthesis ..

Modular Pathway Engineering of Diterpenoid Synthases …

Most nucleotide biosynthesis in most cells occurs via the nearly ubiquitous de novo synthetic pathways, starting from amino acids and their derivatives (see Purine Ribonucleotide Metabolism and Pyrimidine Ribonucleotide Metabolism). However, most cells possess capabilities for taking up nucleosides and nucleobases and converting them to nucleotides. Because these processes involve reutilization of previously synthesized purine and pyrimidine rings, they are called salvage pathways. These pathways are much shorter and simpler than the de novo pathways. On the other hand, there is much more variability from organism to organism, and from tissue to tissue in the same organism, in salvage synthetic capabilities. The metabolic importance of salvage pathways has come to light, first, along with the realization of the serious consequences of hereditary deficiencies in certain salvage enzymes and, second, with the many ways in which salvage pathways are being exploited to create or enhance the effectiveness of chemotherapy against a variety of diseases.

Subsequently carbamoyl phosphate is incorporated into the pyrimidine nucleotide biosynthesis pathway through …

The L-Arginine-Nitric Oxide Pathway

As an example of the factors involved, consider the fluorinated pyrimidines, 5-fluorouracil (FUra) and 5-fluorodeoxyuridine (FdUrd), analogues used for four decades in treating various cancers. It was established in 1958 (9) that these drugs are converted in vivo to 5-fluorodeoxyuridine monophosphate (FdUMP), an analogue of deoxyuridine monophosphate, the substrate for thymidylate synthase (Fig. 1; see Deoxyribonucleotide Biosynthesis And Degradation), and that FdUMP is a potent inhibitor of thymidylate synthase and, hence of DNA replication. Figure 1 shows also the metabolic pathways that both activate these analogues and divert them from their desired endpoint (10). From the figure, one can see that coadministration with FdUrd of a thymidine phosphorylase inhibitor should increase the effectiveness of the analogue by blocking its catabolism. Note that there are multiple routes for activation of FUra; note also that FUra can enter pools of RNA precursors which, in principle, could limit its selectivity by diminishing the specificity of its effect against DNA synthesis. There is evidence, however, that, in some tumors, the effectiveness of FUra actually depends in part on its incorporation into RNA, where it stimulates translational miscoding.

Dysregulation of Purine Nucleotide Biosynthesis Pathways Modulates Cisplatin Cytotoxicity in Saccharomyces cerevisiae

Nucleotide Biosynthesis - heavenforum

We expected that the first step, in which PRPP is synthesized, would besubject to regulation because of the prominence of PRPP in other biosyntheticreactions, including that of pyrimidine nucleotides. Increasing levels of ADPand GDP have a negative feedback effect on the enzyme Ribose phosphatepyrophosphokinase. The enzyme catalyzing the second step of the pathway,Amidophosphoribosyl transferase, is inhibited by all of the adenine and guaninenucleotides, the adenine nucleotides binding to one inhibitory site on theenzyme and the guanine nucleotides to another separate site. This enzyme is also"activated" by the increase in the level of PRPP and this is called a"feedforward activation".