Pentose phosphate pathway - Wikipedia

With the exception of the discussions of purine and pyrimidine nucleotidedegradation, which are generalized to ribonucleotides and deoxyribonucleotides,the biosynthetic pathways that we have looked at were specific toribonucleotides and, therefore, to RNA. Now we want to build upon this todiscuss the components of DNA, the deoxyribonucleotides.

and the biosynthesis pathway diverges depending on ..

The pathway of nucleic acid ribose synthesis in a human carcinoma cell in tissue culture.

Deoxyribose, or more precisely 2-deoxyribose, ..

The key molecule in the synthesis of the pyrimidine ribonucleotides isuridine monophosphate (UMP), as it is the final product of the six-stepsynthesis pathway and from which CTP is subsequently derived. Thepyrimidine ring, in the form of dihydroorotate, is formed first (note that thisis not the case for the pyrimidine bases) following attachment toribose-5-phosphate.

Pentose Phosphate Pathway - an overview | …

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".

such as ribose, for nucleotide synthesis

The body manufactures D–Ribose naturally from glucose via the pentose phosphate pathway. The gate keeping enzymes glucose-6-phosphate dehydrogenase (G–6–Pdhl) and 6–phosphogluconate dehydrogenase (6–PGdh) controls this complex metabolic process. Because the activities of these enzymes are poorly expressed in most body tissues, a delay in D–Ribose synthesis limits cellular energy recovery. Many situations produce a chronic metabolic stress state, leaving cells without the ability to efficiently recycle their energy supply. These stressed cells simply cannot make energy fast enough to keep pace with demand. However, D–Ribose administration significantly accelerates energy recovery, allowing cells to conserve energy substrates and rebuild depleted energy pools.

Pentose Phosphate Pathway - SlideShare

N2 - Human myometrial contraction plays a fundamental role in labor. Dysfunction of uterine contraction is an important cause of failure in progression of labor. The mechanisms of control of uterine contractions are not completely understood. It appears that intracellular Ca2+ mobilization may play an important role during uterine contraction. Several mechanisms of intracellular Ca2+ mobilization have been described. However, in human uterus only the inositol 1,4,5-trisphosphate-induced Ca2+ release has been extensively studied to date. In view of the identification of the presence of functional ryanodine channels in myometrium, we explored the role of the endogenous regulator of the ryanodine channel cyclic-ADP-ribose in human myometrial Ca2+ regulation. Cyclic-ADP-ribose (cADPR) is a naturally occurring nucleotide implicated in the regulation of the gating properties of the ryanodine channel, in fact cADPR may be a second messenger that activates the ryanodine receptor. Here we explore the components of the cADPR system in human myometrium. We found that human myometrium contains all the components of the cADPR pathway including (1) cADPR-activated microsomal Ca2+ release and (2) enzymes responsible for synthesis and degradation of cADPR and, furthermore, that intracellular levels of cADPR were detected in human myometrial tissue. These data indicate that the cADPR system is present and operational in human myometrial tissue. Further research is warranted to determine the role of this new signaling molecule in uterine contraction.

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Nucleosides are composed of a heterocyclic ring (defined as the base) that is attached to a ribose. Addition of a phosphate to a nucleoside, at carbon 5 of the ribose, produces a nucleotide. Nucleotides function as ubiquitous building blocks for the synthesis of all nucleic acids, and also function in enzymatic reactions as cofactors and as a source of energy. These central metabolic roles require their continued biosynthesis from readily available precursors, and this process is defined as nucleotide synthesis. The synthesis of purines starts with ribose‐phosphate, to which are attached the individual atoms of the heterocyclic base in a stepwise fashion. Pyrimidine synthesis starts with the stepwise formation of the base, to which is then added the ribose‐phosphate. Bases and nucleosides may also be recycled in salvage pathways.