Pantetheine phosphate

BaddUey J. Thain, E.M. (1953) Coenzyme A. Part VIII. The Synthesis of Pantetheine 4 -Phosphate (Acetobacter Stimulatory Factor), a Degradation Product of the Coenzyme. Journal of the Chemical Society, 1610-1615. 

Figure 7 Biosynthesis of pantothenate. 54, aspartate 58, spermine 59, uracil 60, pantothenate 65, pantetheine 4-phosphate 66, coenzyme A.

Thiol group, sulfkydryl group, metcapto gro -SH, the functional group of thiols (mercaptans), i.e. the functional group of RSH, where R is the remainder of the molecule. T.g. may be structurally important as in Thiol enzymes (see), or functionally important as in Coenzyme A (see), Pantetheine-4 -phosphate (see), Lipoic acid (see), Thioredoxin (see), etc. The functional form of lipoic and thioredoxin is a dithiol. 

EC 2.7.1.33) to N-(i )-4 -phosphopantothenate. Activation of the carboxylate results from the addition of P-alanine (P-alanine is formed on decarboxylation of aspartate [Asp, D], EC 4.1.1.11), by cytidylate formation (cytosine triphosphate [CTP] is followed by coupling to L-cysteine (Cys, C) (EC 6.3.2.S) to produce N-[(i )-4 -phosphopantothienoyl]-L-< steine. Oxidation to the thioaldehyde with flavin mononucleotide (EMN FMNH2) allows decarboxylation of the latter with the formation of the corresponding enol. Then, reduction with nicotinamide adenine dinucleotide phosphate (NADPH/IT NADP) (EC 4.1.1.36) leads to 4-phosphopantetheine (pantetheine 4 -phosphate). 

Ba-DL-pantetheine-4 phosphate (prepn. s. 172) allowed to react with adenosine-5 -phosphoromorpholidate (added as 4-morpholine N,N -dicyclocarboxamidi-nium salt from its prepn., s. Am. Soc. 83, 649) in anhydrous pyridine, and the... 

A soln. of dibenzyl phosphorochloridate in benzene added to a dry soln. of DL-2 -0,S-dibenzylpantetheine in pyridine, which has been frozen in a Dry Ice-acetone bath, thawed until homogeneous, refrozen, stored overnight at —20°, the crude product dissolved in liq. NH3 containing a little dry methanol, a soln. of Na in liq. NH3 added portionwise until a stable blue color results, and the final product isolated as the Ba-salt Ba-DL-pantetheine-4 phosphate (startg. m. f. 167). Y 78%. J. G. Moffatt and H. G. Khorana, Am. Soc. 83, 663 (1961). 

Ba-D-pantothenonitrile 4 -phosphate and cysleamine refluxed 6 hrs. in methanol under Ng, the resulting crude thiazoline dissolved in water, adjusted to pH 5.0 with 1 N oxalic acid, heated 2 hrs. at 60° under Ng, and the product isolated as the Ba-salt Ba-D-pantetheine 4 -phosphate. Y 82%. F. e. s. O. Nagase, Chem. Pharm. Bull. 15, 648, 644, 655 (1967). 

Coenzyme A biosynthesis NOD of pantetheine-phosphate [E] and [A] 36 Cloned from Homo sapiens, assay, pathway 36... 

Whereas catabolism involves oxidation of starting molecnles, biosynthesis or anabolism involves reduction reactions, hence the need for a reducing agent or hydrogen donor, which is usually NADP (nicotinamide adenine dinucleotide phosphate). These catalysts are known as coenzymes and the most widely occurring is coenzyme A (CoA), made up of ADP (adenosine diphosphate) and pantetheine phosphate. 

Figure 6 Biosynthesis of coenzyme A and acyl-carrier protein. Enzyme I = pantothenate kinase (EC 2.7.1.33) enzyme II = phosphopantothenylcystein synthetase (EC 6.3.2.5) enzyme III = phosphopantothenylcystein decarboxylase (EC 4.1.1.33) enzyme IV = pantetheine phosphate adenyltrasferase (EC 2.7.7.3) enzyme V = dephospho-CoA kinase (EC 2.7.1.24) enzyme VI = transferase.

The chemical structure of coenzyme A is considerably more complex than that of the preceding coenzymes. It is helpful to divide it mentally into adenosines, 5 -diphosphate and pantetheine phosphate. Pantetheine is a growth factor for several microorganisms, e.g. Lactobacillus bulgaricus. It, in turn, consists of pantoic acid, 3-alanine, and mercaptoethylamine, the decarboxylation product of cysteine. The pantetheine component of CoA therefore contains three constituents in amide linkage. 

Like modular PKSs, peptide synthetases also epimerize some substrates and/or intermediates. For example, the starter substrate amino acid of cyclosporin A is D-Ala. Racemization of alanine is not catalyzed by an integrated subunit of cyclosporin A synthetase, but by alanine racemase. This is a separate, pyridoxal phosphate-dependent enzyme [ 193]. In contrast, Grsl and Tycl covalently activate L-Phe as a thioester and subsequently epimerize the amino acid [194]. D-Phe is the only epimer accepted as a substrate for dipeptide formation by Grs2 and Tyc2 [195, 196]. No racemization activity is detected in a pantetheine-deficient mutant of Grsl [197]. Deletion mutagenesis pointed to the requirement of the COOH-terminal part of the module for epimerizing L-Phe to D-Phe [180]. In contrast, the biosynthesis of actinomycin D, a bicyclic chromo-pentapeptide lactone (Fig. 10), involves formation of the dipeptide 6-MHA (methylanthranilic acid)-L-Thr-L-Val prior to epimerization of the L-Val exten-... 

The same method was employed by Baddiley and Thain for the synthesis of pantetheine-2, 4 -hydrogen phosphate (4). 

Pantothenic acid is taken in as dietary CoA compounds and dCphosphopantetheine and hydrolyzed by pyrophosphatase and phosphatase in the intestinal lumen to dephospho-CoA, phosphopantetheine, and pantetheine. This is further hydrolyzed to pantethenic acid. The vitamin is primarily absorbed as pantothenic acid by a saturable process at low concentrations and by simple diffusion at higher ones. The saturable process is facilitated by a sodium-dependent multivitamin transporter, for which biotin and lipoate compete. After absorption, pantothenic acid enters the circulation and is taken up by cells in a manner similar to its intestinal adsorption. The synthesis of CoA from pantothenate is regulated by pantothenate kinase, which itself is subject to negative feedback from the products CoA and acyi-CoA. The steps involved were outlined above. Pantothenic acid is excreted in the urine after hydrolysis of CoA compounds by enzymes that cleave phosphate and the cys-teamine moieties. Only a small fraction of pantothenate is secreted into milk and even less into colostrum. 

Figure 2. Time course for CoA synthesis by dried cells of B. ammoniagenes. CAJ Synthesis from pantothenic acid reaction mixture (1 mL) containing 5 [imol sodium pantothenate, 10 /imol cysteine, IS /imol ATP, 10 y.mol magnesium sulfate, ISO pmol potassium phosphate buffer, pH 6.0, and 100 mg dried cells of B. ammoniagenes was incubated at 37°C with (a) or without (b) 2 mg of sodium hurylbenzenesulfonate. A mixture without sodium pantothenate (c) was used as a control run. (B) Synthesis from pantetheine the reaction conditiotK were the same as those in (A) except that an equimolar amouni of pantethine was used in place of sodium pantothenate.

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. 

Figure I Schematic views of reactions involved in peptide biosynthesis. (1) Adenylate formation involving nucleophilic attack of the carboxyl group at the a-phosphate of the MgATP --complex with release of MgPP. - (2) aminoacylation of the pantetheine cofactor by formation of the thio-late anion, attack of the mixed anhydride, and release of AMP (3) tentative view of the peptide bond formation by nucleophilic attack of the aminoacyl-nitrogen at the preceding thioester-car-boxyl, involving deprotonaiion-protonation (4) epimerization of an aminoacyl-thioester, a reaction differing from those catalyzed by the well-characterized amino acid racemases. (Altered from Ref. 13. )...

The synthesis of coenzyme A can be divided into the synthesis of adenosine (adumbrated above) and the synthesis of pantotheine phosphate. The latter is then conveniently divided into the preparation of pantothenic acid and its subsequent conversion to the desired (pantetheine) thiol. 

Structure of Coemyme A. The elucidation of the structure of CoA depended heavily on d radation by specific enzymes. The phosphate on carbon 3 of the adenosine was shown to be a monoester phosphate by hydrolysis with prostate phosphomonoesterase. The localization of the monoester at the 3 position was established by its sensitivity to a b nucleotidase that attacks only nucleoside 3 -pbosphates, not 2 - or 5 -phosphates. The original CoA molecule or the phosphatase product, depbospho CoA, can be split by nucleotide pyrophosphatases from potato or snake venom. These reactions permitted the identification of the adenosine phosphate portion of the molecule. The position of the phosphate on pantothenic acid cannot be determined enzymatically, but was established by studies on the synthesis of CoA from synthetic phos-phorylated pantetheines. Pantetheine is split to thiolethanolamine and pantothenic acid by an enzyme found in liver and kidney. This enzyme also attacks larger molecules, including CoA. 

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