Dephospho-CoA kinase

CARNOSINE SYNTHETASE CHAPERONES CHOLINE KINASE CHOLOYL-CoA SYNTHETASE COBALAMIN ADENOSYLTRANSFERASE 4-COUMAROYL-CoA SYNTHETASE CREATINE KINASE CTP SYNTHETASE CYTIDYLATE KINASE 2-DEHYDRO-3-DEOXYGLUCONOKINASE DEHYDROGLUCONOKINASE DEOXYADENOSINE KINASE DEOXYADENYLATE KINASE DEOXYCYTIDINE KINASE (DEOXYjNUCLEOSIDE MONOPHOSPHATE KINASE DEOXYTHYMIDINE KINASE DEPHOSPHO-CoA KINASE DETHIOBIOTIN SYNTHASE DIACYLGLYCEROL KINASE DIHYDROFOLATE SYNTHETASE DNA GYRASES DNA REVERSE GYRASE ETHANOLAMINE KINASE EXONUCLEASE V... 

DIETHYL PYROCARBONATE DEPHOSPHO-CoA KINASE Dephospho-CoA pyrophosphorylase, PANTETHEINE-RHOSRHATE ADENYLYL-TRANSFERASE DEPOLARIZATION ACTION ROTENTIAL HYPERROLARIZATION DEPOLYMERIZATION PROCESSIVITY... 

Figure 12.2. Biosynthesis of coenzyme A. Pantothenate kinase, EC 2.7.1.33 phosphopantothenylcysteine synthase, EC 6.3.2.5 phosphopantothenylcysteine decarboxylase, EC 4.1.1.36 phosphopantetheine adenyltransferase, EC 2.7.7.S and dephospho-CoA kinase, EC 2.7.1.24. CoASH, free coenzyme A.

Phosphopantetheine undergoes adenylyl transfer from ATP to yield de-phospho-CoA, which is then phosphorylated at the 3 position of the ribose moiety to yield CoA. Phosphopantetheine adenylyltransferase and dephos-pho- CoA kinase activities occur in a single bifunctional enzyme, which is found in both cytosol and mitochondria. However, in addition to the bifunctional protein, human tissues also contain a separate dephospho-CoA kinase (Begley et al., 2001 Zhyvoloup et al., 2002). 

Dephospho-CoA kinase (DPCK EC 2.7.1.24) catalyzes the selective MgATP-dependent phosphorylation of the 3 -hydroxyl of the ribose moiety dephospho-CoA 11 to form CoA 1, the final product of the biosynthetic pathway (Equation (7)). As pointed out in the previous section, most eukaryotic organisms have the DPCK activity located with PPAT on a bifunctional protein referred to as CoA synthase. However, unlike PPAT, the DPCK domain of this protein exhibits good sequence homology with its bacterial counterparts. In A. thaliana, the protein is monofunctional. ... 

Fig. 187. Biosynthesis of coenzyme A 1 Pantothenate synthetase, pantothenate kinase 2 phosphopantothenoylcysteine synthetase 3 phosphopantothenoylcysteine decarboxylase 4 dephospho-CoA synthetase 5 dephospho-CoA kinase...

Dephospho-CoA pyrophosphorylase. 4-phosphopanto-thenate was prepared from dephospho-CoA by incubation with commercial nucleotide pyrophosphatase, and isolated by affinity chromatography with Thiopropy1-Sepharose followed by preparative paper chromatography. Dephospho-CoA pyrophosphorylase was estimated at pH 8.5, in a system similar to that used for dephospho-CoA kinase. 

Table 4 shows that this increase of biosynthesis cannot be explained by an increase of the main, supernatant pool of dephospho-CoA kinase. Table 4 also shows a mitochondrial pool of dephospho-CoA kinase, which we also demonstrated in earlier studies (4,5). This activity was also similar in the normal and the drug-exposed group. 

Mitochondrial dephospho-CoA kinase (8) has a rather broad pH-optimum of about 8.5, and is dependent on Mg " (full activation is achieved at 0.5 mmol/1). Its... 

Biosynthesis of CoA from pantothenic acid in the supernatant fraction of the liver. All enzymes required for the biosynthesis of CoA from pantothenic acid have been isolated from the soluble fraction of the cell (8). By using the vitro system of Abiko (cf. 8) for the synthesis of CoA from pantothenic acid, we found the capacity for CoA-biosynthesis to be markedly increased after treatment with clofibrate (2). Dephospho-CoA kinase was not significantly (or only very slightly) increased, but the activity of pantothenate kinase was more than doubled. CoA will exert feed-back inhibition of pantothenate kinase (8), and the extent of this inhibition was not changed by clofibrate (2). 

Mitochondrial biosynthesis of CoA. We have previously reported that dephospho-CoA kinase is present in mitochondria from liver (2,5,9) and kidney (4). Even though it has been generally thought that the inner mitochondrial membrane is a permeability barrier for CoA (cf. 5), the existence of a separate, mitochondrial pathway for the biosynthesis of CoA has to our knowledge not been suggested. 

In this study, we have found that both enzymes representing the last two steps in the biosynthesis of CoA - dephospho-CoA pyrophosphory1ase and dephospho-CoA kinase - are present in the inner mitochondrial membrane. Pantothenate kinase - representing the first step in the biosynthesis of CoA - is not detectable in reason-... 

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