Synthesis of niacin nucleotides from the beginning.

compared with radon synthesis, the head-to-head synthesis of nucleotides is simpler, isotope tracer proves that the N1, C4, C5 and C6 that make up the ring are provided by winter acid, C3 comes from CO2 and N3 comes from glutamine. (Figure 8-7).·1​Figure 8-7 the source of the raw material for the synthesis of the ringthe synthesis of the nucleotide is first synthesized into the ring, and then connected with phosphate kerucleose.1. Synthesis of urine nucleotides (UMP) is done by a 6-step reaction: (Figure 8-8)Figure 8-8 UMP biosynthetic(1) Synthesis of carbamoyl phosphate: The first step in the synthesis of acetate is the production of aminomethyl phosphate, which is produced by the anatomic methyl phosphate synthesis enzyme II. (carbamoyl phosphate synthetase II., CPS-II.) catalytic CO2 and glutamine. As < discussed in the metabolism of > amino acids, aminomethyl phosphoric acid is also the starting material for urea synthesis. However, the amino methyl phosphoric acid required in urea synthesis is catalyzed synthesis by CPS-I. in the liver mitochondrials, with NH3 as the nitrogen source, while the amino methyl phosphoric acid in the synthesis is generated by CPS II. catalysis in the cytoplasm, which provides nitrogen sources using glutamine. A comparison of CPS-I.and CPS-II. can be found in Table 8-1 below.(2) synthetic methylmate (carbamoyl aspartate): by the winter arginine Aspartate transcarbamoylase (ATCase) catalyses the contraction of methylphenidate with aminomethylphosphate to produce carbamoyl aspartate. This reaction is a speed limit step for synthesized. ATCase is a speed-limiting enzyme that is inhibited by feedback from the product. Does not consume ATP and is hydrolysed by aminomethyl phosphate.8-1 comparison of two amino methyl phosphate synthasesthe mitochondrials reflect the liver) . nosynthesized withamino Methyl phosphate synthase I.amino methyl phosphate synthase II.distributioncells (all cells)nitrogen sourceamineglutaminen acetyl glutamate UMP (mammals) function urea synthesis (3) closed-loop production of dihydroeloxyclic acid (dihydroolorotase): catalytic aminomethyl chlorosteine dehydration, molecular re-discharge to form a dihydroctic whey acid with a ring. (4) oxidation of dihydroclic whey acid: catalytic by dihydroorotate dehyologenase, dihydro-whey acid oxidation to produce whey acid (orotate). This enzyme requires FMN and non-hemolybin Fe2 plus, located on the outer side of the membrane in the mitochondria, provides oxidation capacity by quinones, and the remaining 5 enzymes in the synthesis of niacin are present in the cell fluid. (5) to obtain phosphate kerucleose: by whey acid phosphate PV transfer enzyme catalytic whey acid and PRPP reaction, the production of whey acid nucleotides (orotidine-5-monophosphate, OMP) Water supply by PRPP hydrolysing. (6) dehydration to generate UMP: UMP is produced by OMP decarboxylase catalytic OMP dehydration. Jones and other studies have shown that the first three enzymes that catalyz the synthesis of the above-mentioned synthesizing in animals, namely CPS-II., tycholine aminomethyl transferase and dihydro-whey acidase Located on the same peptide chain with a molecular weight of about 210kD, it is a versatile enzyme; Similarly, enzymes that react (5) and (6) (whey acid phosphate kerucleose transferase and OMP decarbonase) are also located on the same peptide chain. Reactions (3), (4), (6), reactions (7) and (8) and reactions (10) and (11) are also multi-functional enzymes. The intermediates of these multifunction enzymes are not released into the medium, but move between successive enzymes, a mechanism that accelerates the total speed of multi-step reactions while preventing the destruction of other enzymes in cells. 2.UTP and CTP synthesis the synthesis of ureatide triphosphate (UTP) is similar to the synthesis of terophosphate nucleosides. cytosine triphosphate (CTP) is produced by CTP synthase (CTP synthetase) catalytic UTP ammonia. (Figure 8-9) In animals, amino is provided by glutamine and in bacteria it is provided directly by NH3. This reaction consumes 1 molecule ATP. Figure 8-9 by UTP synthesis CTP 3. The regulation synthesized from the head of the nucleotide is the main regulatory enzyme synthesized from the head by the acetaminophen aminomethyl transferase (ATCase) in bacteria. In E. coli, ATCase is activated by atTP is variant, and CTP is its variant inhibitor. In many bacteria, UTP is the main variant inhibitor of ATCase. in animal cells, ATCase is not a regulator enzyme. The synthesis of niacin nucleotides is mainly regulated by CPS-II. UDP and UTP inhibit their activity, while ATP and PRPP are their activators. The second level of regulation is OMP deoxymease, UMP and CMP as its competitive inhibitors. (Figure 8-10) in addition, the generation of OMP is affected by PRPP. Figure 8-10 synthesized adjustment net 4. milk Orotic aciduria Whey acid uremia is a genetic disease, mainly manifested in the discharge of large amounts of whey acid in the urine, growth delay and severe anemia. This is due to defects in the dual-functional enzymes that catalytic nucleotide synthesis reactions (5) and (6) from the beginning. Clinical treatment with urine or cytosine.