Cytidine 5 -triphosphate CTP

Fig. 4.3.2 Human sialic acid metabolism and genetic defects. -6P -6-Phosphate, -9P -9-phos-phate, CMP cytidine 5 -monophosphate, CTP cytidine 5 -triphosphate, UDP-GlcNAc uridine diphosphate-N-acetyl-D-glucosamine, ManNAc N-acetylmannosamine, NeuAc N-acetylneur-aminic acid, OGS oligosaccharides, SASD sialic acid storage disease...

R-O-P can react with the related high energy nucleoside triphosphate CTP (cytidine 5 -triphosphate) ... 

CT-1, cardiotrophin-1 CTNF, ciliary neurotrophic factor CTP, cytidine 5 -triphosphate Cyclic AMP, adenosine 3, 5 -cyclic monophosphate... 

Scheme L Synthesis of a2,64inked sialyl-N-acetyllactosamine using a one-pot multi-enzyme system with in situ regeneration of CMP-Neu5Ac. Abbreviations for enzymes CSS, CMP-sialic acid synthetase NMK, nucleoside monophosphate kinase PK, pyruvate kinase PPase, pyrophosphatase. Abbreviations for compounds PEP, phosphoenolpyruvate ADP, adenosine 5 -diphosphate ATP, adenosine 5 -triphosphate CMP, cytidine 5-monophosphate CDP, cytidine 5 -diphosphate CTP, cytidine 5-triphosphate LacNAc, N-acetyllactosamine NeuSAc, N-acetylneuraminic acid PPi, inorganic pyrophosphate.

CoA, coenzyme A dephospho-CoA, 3 -dephospho-coenzyme A P-pantothenic acid, 4 -phosphopantothenic acid P-pantothenoyl-cysteine, 4 -phosphopantothenoylcysteine P-pantetheine, 4 -phos-phopantethelne ATP, adenosine 5 -triphosphate ADP, adenosine 5 -dlphosphate AMP, 5 -adenyllc acid CTP, cytidine 5 -triphosphate CMP, 5 -cytldylic acid GTP, guanosine 5 -triphosphate GMP, 5 -guanylic acid ITP, inosine 5 -triphosphate UTP, uridine 5 -tri-phosphate PPl, inorganic pyrophosphate. 

CMP = oytidine monophosphate, CTP = cytidine 5 -triphosphate, LDH = lactate dehydrogenase ADH = alcohol dehydrogenase... 

CMP-KDO synthetase (cytidine-5 -triphosphate cytidine-5 -mon-ophosphate-3-deoxy-D-manno-octulosonate cytidylyltransferase), the next enzyme in the pathway, catalyzes the formation of the nucleotide sugar, CMP-KDO from CTP and KDO. This enzyme was first studied by Ghalambor and Heath (IT). We have purified this enzyme to homogeneity (27). T i apparent K values for CTP nd KDO in the presence of 10 mM Mg were determined to be 2 x 10 M and 2.9 x 10 M, respectively. The enzy tic reaction was dependent upon the addition of CTP, KDO and Mg but did not require a reducing agent. The formation of CMP-KDO was not inhibited by the addition of CDP, CMP, KDO-8-phosphate or N-acetylneuraminic acid to the complete reaction mixture. In agreement with Ghalambor and Health (17), neither KDO-8-phosphate nor N-acetylneuraminic acid could substitute for KDO in the reaction mixture. Pyrophosphate, one of the end products, is a weak inhibitor of the reaction with an apparent Ijq value of 5.0 mM. The addition of CMP,CD or any of the other mono- or di-nucleotides did not inhibit the reaction. 

The corresponding ribonucleosides are adenosine, guanosine, cytidine and uridine. The corresponding ribonucleotides are adenosine 5 -triphosphate (ATP), guanosine 5 -triphosphate (GTP), cytidine 5 -triphosphate (CTP) and uridine 5 -triphosphate (UTP). 

In this experiment we will examine some of the properties of the aspartate transcarbamylase of Escherichia coli, which is typical of many enzymes subject to feedback inhibition and which has been studied extensively. Aspartate transcarbamylase (ATCase) catalyzes the first reaction unique to the biosynthesis of pyrimidine nucleotides. ATCase is subject to specific inhibition by quite low concentrations of one of its end products, cytidine 5 -triphosphate (CTP). This relationship and two other regulatory interactions important to the control of pyrimidine biosynthesis are summarized in Figure 9-1. 

Dynamics of proteins are in general important to their functions (Frauenfelder et al. 1979 Karplus and McCammon, 1983, Capeillere-Blandin and Albani, 1987). It was shown for example, that binding of cytidine 5 -triphosphate (CTP) and N-(phosphonoacetyl)-L-aspartate (PALA) to aspartate transcarbamylase (ATCase) from Escherichia coli induces a modification in the dynamics behavior of the two Trp residues of the protein (Royer et al. 1987). 

Cytidine 5 -triphosphate synthase (CTPS, EC 6.3.4.2) catalyzes the formation of cytidine 5 -triphosphate (CTP) from uridine 5 -triphosphate (UTP), the last committed steps in pyrimidine nucleotide biosynthesis (Scheme 50) [178, 179]. The reaction proceeds by an ATP-dependent phosphorylation and requires ammonia. CTPS is a relevant target in some forms of cancers (i.e. non lymphocytic leukaemia) [180],... 

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... 

A major advance in the understanding of the biosynthesis of the glycerophos-phatides was the discovery by Kennedy and Weiss (1956) of the role of nucleotides of cytosine in the biosynthesis of the glycerophosphatides. Cytidine 5 -triphosphate (CTP) was shown to be necessary for the incorporation of phosphorylcholine into lecithin by liver preparations. Similar observations have been reported for brain (McMubbay et al. 1957, Stbickland et al. 1963) and other tissues. The nucleotide requirement is specific for CTP, none of the other nucleoside 5 -triphosphates being active. Kennedy and Weiss (1956) showed that CTP combines with phosphorylcholine to form the intermediate CDP-choline (IV) according to the equation ... 

Abbrewiaiions ADP. adenosine 5 -dlphosphate. ATP. adenosine S -triphosphate CDP. cytidine S -dlphosphate CMP, idine 5 -monophosp1iate CTP, cytidine 5 -lriphosphate. NADP. nicotinamide adenine dinucleotide phosphate (oxidised form) NADPH. nicotinamide adenine dinucleolide phosphate (reduced form) DPPi, pyrophosphate... 

Figure 10 Chemical structures of adenosine 5 -monophosphate (n = 1 AMP ), adenosine 5 -diphosphate (n = 2 ADP "), and adenosine 5 -triphosphate (n = 3 ATP ) as well as of cytidine 5 -monophosphate (n = 1 CMP, cytidine 5 -diphosphate (n = 2 CDP ), and cytidine 5 -triphosphate (n = 3 CTP ) in their dominating anti conformation [11-14,50]. Note, the triphosphate chain in nucleoside 5 -triphosphates (NTP ) is labeled a, P, and y, where y refers to the terminal phosphate group (see also Figure 9) for nucleoside 5 -diphosphates (NDP ) the situation is analogous with a and P (see Figure 9). The adenine and cytosine residues in the nucleotide structures shown above may be replaced by one of the other nucleobase residues shown in Figiue 1 if this substitution is done in the way the bases are depicted within the plane (Figure 1), then the anti conformation will also result for the corresponding nucleoside 5 -phosphates. The abbreviations AMP, ADP , ATP , IMP, etc. in this text always represent the 5 -derivatives 2 - and 3 -derivatives are defined by 2 AMP, 3 AMP, etc. in a few instances where uncertainties might otherwise occur, the abbreviations 5 AMP , 5 ADP , etc. are also used.

Figure 20.9 The positions in the pathway for de novo pyrimidine nucleotide synthesis where GLUCOSE provides the ribose molecule and GLUTAMINE provides nitrogen atoms. Glucose forms ribose 5-phosphate, via the pentose phosphate pathway (see chapter 6), which enters the pathway, after phosphorylation, as 5-phospho-ribosyl 1-pyrophosphate. Glutamine provides the nitrogen atom to synthesise carbamoylphos-phate (with formation of glutamate), and also to form cytidine triphosphate (CTP) from uridine triphosphate (UTP), catalysed by the enzyme CTP synthetase. It is the amide nitrogen of glutamine that is the nitrogen atom that is provided in these reactions.

Reagents. Aqueous ethanol solutions of the triethylammonium salts of adenosine-5 -[a-S2P]triphosphate (a- PATP), adenosine-5 -[7-S2P]triphosphate (7-S2P-ATP), thymidine-5 -[a-S2P]triphosphate (a- p-TTP), cytidine-5 -[q-S2P]triphosphate (a-S2P-CTP), and guanosine-5 -[a-S2P]triphosphate (a-S2P-GTP) were purchased from Amersham (Arlington Heights, IL). Radioactive sample concentrations reported for detector efficiency determination were adjusted from the manufacturer s specifications after subjecting several diluted aliquots of the stock solution to liquid scintillation counting. 

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