Cytidine 5 -phosphate, structure

Ultrasonic relaxation techniques have been used to estimate the energy barrier to syn-anti conformational interconversion in cytidine 2, 3 -mono-phosphate, in the presence and absence of ethidium bromide. Raman spectroscopic measurements on a number of dinucleoside monophosphate crystals of precisely known sugar-phosphate structure have been compared with those of B- and A-form DNA, to give information on the comparative rigidity of the backbone in the nucleic acids. The same technique, applied to poly(dA-dT) and poly[d(A-T)] at different temperatures, suggests that some of the furanose... 

Further examples of conformational adaptationf will be given, each one quite individual in its mechanism, yet collectively supplying a picture of considerable uniformity. Ribonuclease forms a compact structure, hydrophilic outside, lipophilic inside, with a slot to receive the substrate. The active site makes use of histidine residues (numbers 12 and 119) that would otherwise be remote from one another (Kartha, Bello and Marker, 1967). The dimensions of the folded ribonuclease molecule are about 30X 30X 38 A (mol. wt. 15 000). When charged with a substrate, e.g. cytidine phosphate, one histidine residue binds the phosphate group, the other the sugar. The tertiary structure of a-chymotrypsin has been similarly worked out the active site depends on the closeness of two amino acids that are on different strands, namely serine-195 and histidine-57... 

Cytidine phosphates cytidine S -monophosphate (CMP, cytidylic acid, M, 323.2), cytidine 5 -diphos-phate (CDP, M, 403.19) and cytidine 5 -triphosphate (CTP, M, 483.16). For structure, see e. g. Pyrimidine biosynthesis. CTP is a precursor of RNA synthesis, while deoxy-CTP is a precursor of DNA synthesis. CDP may be regarded as the coenzyme of phospholipid biosynthesis (see Membrane lipids) (activated choline is CDP-choline). Glycerol and the sugar alcohol, ribitol, are also activated by bonding to CDP (see Nucleoside diphosphate sugars). Reduction of ribose... 

Cytosine was isolated from hydrolysis of calf thymus in 1894 and by 1903 its structure was known and it had been synthesized from 2-ethylthiopyrimidin-4(3H)-one. The acid hydrolysis of ribonucleic acid gives nucleotides, among which are two cytidylic acids, 2 -and 3 -phosphates of cytidine further hydrolysis gives cytidine itself, i.e. the 1-/3-D-ribofuranoside of cytosine, and thence cytosine. The deoxyribonucleic acids likewise yield deoxyribonucleotides, including cytosine deoxyribose-5 -phosphate, from which the phosphate may be removed to give cytosine deoxyriboside and thence cytosine. 

The structure shown was confirmed by the identification of cytidine 5 -phosphate and N-acetylneuraminic acid after mild acidic hydrolysis, and by the stability of the derivative on treatment with sodium borohydride. Comparison of the optical rotation of the starting derivative182 (44), the products of its hydrolysis,182 and the anomeric... 

The structure of an unusual compound isolated from spores of Ustilago avenue46 has not yet been completely clarified. According to data available,189 it seems to be a cytidine 5 -(D-glucosyl phosphate) derivative having a peptide chain attached to a hydroxyl group of the D-ribose residue. 

Differences in the IR spectra of cytosine, cytidine, and cytidylic acid were considered by Angell.41 This author concluded that the cytidylic acids exist in the solid state in a zwitterion form with one of the hydrogen atoms from the phosphate group at N-3 of the cytosine ring (cf.refs.53,54). Previously Miles 44 postulated that the form 7a rather than the form 8 was the structure of cytidine in acid solution. This conclusion is essentially the same as that of Tsuboi et al.i7 who proposed form 7b for the protonated form of cytidine, as 7a and 7b are two canonical forms of the same tautomer (7). 

The substituents at the 5 or 6 position of the pyrimidine base have no relation to the susceptibility to RNase T2. Madison and Holley 93) have shown that RNase T2 is able to split the phosphodiester bonds of pseudouridylic acid and 5,6-dihydrouridylic acid. Recently, Saneyoshi et al. 86) have found a new minor constituent, Vp, with 5-methyl cytidine 3 -phosphate and other mononucleotides on the two-dimensional paper chromatogram of RNase T2 exhaustive digest of E. coli tRNAVal later the structure of V was proved to be uridine-5-oxyacetic acid 94). 

Molecules with structures as diverse as carbamoyl-phosphate, tryptophan, and cytidine triphosphate are feedback inhibitors of the E. coli glutamine synthase. The feedback inhibition is cumulative, with each metabolite exerting a partial inhibition on the enzyme. Why would complete inhibition of the glutamine synthase by a single metabolite be metaboli-cally unsound ... 

If we attach the nitrogenous bases to a ribose, we have the RNA nucleosides. The four RNA nucleoside bases are adenosine, uridine, cytidine, and guanosine. Usually, these nitrogenous bases are represented as A, U, C, and G, respectively. Figure 12.69 gives the names and structures of these compounds. Addition of a phosphate group to carbon 5 of the ribose sugar affords the RNA nucleotide bases. 

The crystal structure of cytidine-3 -phosphate (monoclinic) [CYTIAC01]... 

The structures of these cytidine nucleotides were confirmed by synthesis. Condensation of 1,2-0-isopropylidene-L-glyceritol 3-phosphate with cytidine 5-phosphate in the presence of dicyclohexylcarbodiimide, followed by careful acid hydrolysis of the isopropylidene group, yielded cytidine glyceritol pyrophosphate identical with the natural product. 

---