Nucleotide kinases

UTP is formed from UMP by two reactions catalyzed by nucleotide kinases that use ATP as the phosphate donor. 

The cofactors are structurally similar. The catalytic mechanisms of nucleotide kinases and sulfotransferases are also similar. 

Figure 9.46. Structures of Adenylate Kinase and Guanylate Kinase. The nucleoside triphosphate-binding domain is a common feature in these and other homologous nucleotide kinases. The domain consists of a central P-pleated sheet surrounded on both sides by a helices (highlighted in purple) as well as a key loop (shown in green).

FIG. 6.13 Mammalian pyrimidine salvage and interconversion pathways. Enzymes listed in Figs 6.13-6.17 are as follows (1) deoxyCMP deaminase (2) thymidylate synthase (3) ribonucleotide reductase (4) deoxyuridine triphosphatase (5) CTP synthetase (6) nucleotide kinase (7) deoxyTMP kinase (8) nucleotide diphosphokinase (9) non-specific phosphatase or nucleotidase (10) cytidine kinase (11) pyrimidine phos-phorylase or hydrolase (12) uracil PRTase (13) cytidine deaminase (14) thymidine kinase (15) cytidine phosphotransferase (16) uridine phosphotransferase (17) thymidine phosphotransferase (18) deoxyribo-nucleotide phosphotransferase (19) cytosine PRTase. 

Griffiths, M.M. Bernofsky, C. Purification and properties of reduced di-phosphopyridine nucleotide kinase from yeast mitochondria. J. Biol. Chem., 247, 1473-1478 (1972)... 

An especially Interesting case of nucleotide - protein recognition Is presented by a group of enzymes which use all four pyrimidine and purine nucleotides as substrates or effectors of the same process key enzymes of cell proliferation such nucleotide kinases, ribonucleotide reduc-... 

The nucleotide kinases apparently serve to distribute throughout the free nucleotide pool the high-energy phosphoryl groups generated by mitochondrial oxidative phosphorylation and substrate level phosphorylations. 

Recently, a universal enzyme-coupled fluorescence assay for glycosyl transferases was developed. This method is extremely cost-effective and is based on the quantification of nucleotides produced in the glycosyl transfer reaction. The guanosine diphosphate (GDP), uridine diphosphate (UDP), and cytidine monophosphate (CMP) are phos-phorylated with nucleotide kinase in the presence of excess of ATP, generating ADP. Via coupled enzyme reactions involving ADP-hexokinase,glucose-6-phosphate dehydrogenase, and diaphorase, the ADP is utilized for the conversion of resazurin to resorufin, which is then quantified by fluorescence measurement. 

The studies with AR and dAR in these ADA deficient red cells have given results identical with previous studies in normal erythrocytes where ADA deficiency was simulated using the inhibitor erythro-9 (2 hydroxy-3-nonyl) adenine EHNA. They confirm that AR and, to a lesser extent, dAR, can be converted by the ADA deficient erythrocyte to the three corresponding nucleotides in roughly the same proportion (10 1.0 0.1) presumably by the same nucleotide kinases. 

Nucleotide Kinases. To generate UTP biologically a uridine nucleotide must first be formed. The synthesis of UMP will be discussed later. A kinase partially purified from calf liver catalyzes the phosphorylation of... 

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