BioCmetza

Purine catabolism pathway is one of the Nucleic acid Metabolism. Because nucleic acids are ubiquitous in cellular material, significant amounts are ingested in the diet. Nucleic acids are degraded in the digestive tract to nucleotides by various nucleases and phosphodiesterases. Nucleotides are then converted to nucleosides by base-specific nucleotidases and nonspecific phosphatases.            Nucleosides are hydrolyzed by  Nucleosidases  or  Nucleoside phosphorylases  to release the purine base. NMP + H2O           →     Nucleoside + Pi The pentoses liberated in these reactions provide the only source of metabolic energy available from purine nucleotide degradation. Feeding experiments using radioactively labeled nucleic acids as metabolic tracers have demonstrated that little of the nucleotide ingested in the diet is incorporated into cellular nucleic ac...

Animal cells degrade pyrimidine nucleotides ( Pyrimidine Catabolism  Pathway) to their component bases. These reactions, like those of purine nucleotides, occur through Dephosphorylation, Deamination and Glycosidic bond cleavages. After  Pyrimidine biosynthesis ,  the newly synthesized molecules undergoes degradation after certain period. Pyrimidine Catabolism Steps: The catabolism of pyrimidine nucleotides are explained in few steps. Step 1: CMP, UMP and deoxyIMP is converted into Cytidine, Uridine deoxythymidine. This reaction is catalyzed by the enzyme Nucleotidase. Step 2: Cytidine is deaminated into Uridine. This reaction is catalyzed by “Cytidine deaminase”. Step 3: Uridine and deoxy thymidine (in case of DNA) is converted into Uracine and Thymidine. This reaction is catalyzed by Uridine phosphorylase. Here on inorganic phosphate is substituted on the first carbon of hydrolyzed Glycosidic linkage sugar molecule. The sugar molecule is relea...

The  pyrimidine synthesis  is a similar process than that of Purines( Purines Synthesis ). In the de novo synthesis of Pyrimidines, the ring is synthesized first and then it is attached to a ribose-phosphate to for a  pyrimidine nucleotide . Pyrimidine rings are assembled from bicarbonate, aspartate and Ammonia. The  pyrimidine biosynthesis  (de novo pyrimidine synthesis pathway) was first observed in mutants of bread mole  Neurospora Crassa , which are unable to synthesize pyrimidine, therefore, require both cytosine and Uracil in their growth medium. Source of Atoms in Pyrimidine Ring: N1, C4, C5 and C6  → Comes from Aspartate N3   → Comes from Glutamine C2   → Comes from HCO 3 –  (Carbonic acid) Steps of Pyrimidine Synthesis: This is one of the nucleic acid synthesis pathways. In the Pyrimidines, there are three Nucleotide molecules; they are UTP, CTP and TTP. The De novo pyrimidine synthesis pathway can be...

In biochemistry, eicosanoids (preferred IUPAC name icosanoids) are signaling molecules made by oxidation of 20-carbon fatty acids. They exert complex control over many bodily systems such as In growth during and after physical activity, Inflammation or immunity after the intake of toxic compounds and pathogens, and act as messengers in the central nervous system. The networks of controls that depend upon eicosanoids are among the most complex in the human body. The first step in the formation of eicosanoid mediators consists in the release of the precursor fatty acids from the membrane phospholipids. This release may happen along several possible metabolic routes (Figure 1.1-1a). How Eicosanoids are synthesizing in Human body: Figure 1.1-1: a) Alternate pathways of Arachidonic acid release b) cellular locations of enzymes involved in Eicosanoid formation   a: Arachidonic acid may be directly released by phospholipase A 2  (PLA 2 ), or alternatively by the s...