Pantothenic structure

Common Name Calcium D-panthothenate Calcium pantothenate Structural Formula ... 

Figure 1 shows the structure of pantothenic acid ((R)-(+)-N-(2,4-dihydroxy-3,3 -dimethyl-1 -oxobuty 1-13-alanine). Only D(+)-pantothenic acid occurs naturally and is biologically active. The alcohol (R)-pantothenol (= (D)-panthenol) shows biological activity as well. 

Pantothenic Acid. Figure 1 Structure of pantothenic acid. 

FIGURE 10.8 Structural formula of P-alanine and pantothenic acid. 1 — P-[3- H]alanine, 2 — D-[3- H]pantothenic acid, 3 — D-[l- C]panthothenic acid. Boldfaced letter H or C denotes radioactivity. 

Pantothenic acid (6.25) is a dimethyl derivative of butyric acid linked to / -alanine. Pantothenate is part of the structure of co-enzyme A (CoA), and... 

Pantothenic acid is a component of coenzyme A, which functions in the transfer of acyl groups (Figure 28.17). Coenzyme A contains a thiol group that carries acyl compounds as activated thiol esters. Examples of such structures are succinyl CoA, fatty acyl CoA, and acetyl CoA. Pantothenic acid is also a component of fatty acid synthase (see p. 182). Eggs, liver, and yeast are the most important sources of pan tothenic acid, although the vitamin is widely distributed. Pantothenic acid deficiency is not well characterized in humans, and no RDA has been established. 

Fig. 1. Structure of CoA, composed of three parts a nucleotide pan derived from 3 -adenosine-5 -pbosphate, forming a phosphodiester bond with a 4-phospho derivative of pantothenic acid, and a third pan derived horn the amino acid, cysteine. The side chain SH group of the latter is ftee in this compound and is readily acylated, and thus able to act as a carrier for acyl groups in biochemical reactions in which it transfers that group between two substrates...

In 1940, Hams, Folkers, ct al. reported structure determination and synthesis and crystallization of pantothenic acid. In 1950. Lipmaiin el al. discovered coenzyme A and, in 1951, Lynen characterized the coenzyme A structure,... 

Phosphopantetheine coenzymes are the biochemically active forms of the vitamin pantothenic acid. In figure 10.11, 4 -phosphopantetheine is shown as covalently linked to an adenylyl group in coenzyme A or it can also be linked to a protein such as a serine hydroxyl group in acyl carrier protein (ACP). It is also found bonded to proteins that catalyze the activation and polymerization of amino acids to polypeptide antibiotics. Coenzyme A was discovered, purified, and structurally characterized by Fritz Lipmann and colleagues in work for which Lipmann was awarded the Nobel Prize in 1953. 

Structures of the vitamin pantothenic acid (in red) and coenzyme A. The terminal —SH (in blue) is the reactive group in coenzyme A (CoASH). 

In contrast to mammals, /i-alanine 3 is generated in Escherichia coli [12] mainly by decarboxylation of L-aspartate 4 [13] (Scheme 1.6.3). The tetrameric enzyme, l-aspartate-a-decarboxylase (EC 4.1.1.15), was isolated from E. coli [13], cloned [14], and its crystal structure [15] was determined. In bacteria, pantothenate synthase converts /(-alanine to pantothenate, a constituent of coenzyme A [16],... 

The uptake and accumulation of various amino acids in Lactobacillus arabinosus have been described. Deficiencies of vitamin B6, biotin, and pantothenic acid markedly alter the operation of these transport systems. Accumulation capacity is decreased most severely by a vitamin B6 deficiency. This effect appears to arise indirectly from the synthesis of abnormal cell wall which renders the transport systems unusually sensitive to osmotic factors. Kinetic and osmotic experiments also exclude biotin and pantothenate from direct catalytic involvement in the transport process. Like vitamin B6, they affect uptake indirectly, probably through the metabolism of a structural cell component. The evidence presented supports a concept of pool formation in which free amino acids accumulate in the cell through the intervention of membrane-localized transport catalysts. 

Therefore, the three vitamin deficiencies so far studied in detail appear to affect amino acid transport and accumulation in similar but indirect ways. The accumulation defect is most pronounced in vitamin B6-deficient cells, for which there is also strong evidence implicating an abnormality in cell wall composition as a likely source of the change in transport activity. Direct evidence for a cell wall change in biotin- and pantothenate-deficient cells has not yet been obtained. The possibility remains, therefore, that the change in accumulation activity may be caused by an abnormality in some other structural component such as the peripheral cell membrane. 

In the biosynthesis of coenzyme A from pantothenate, a five-step process is required, which results in the attachment to pantothenate of the active -SH group and an adenine dinucleotide group. This set of reactions is summarized in Figure 10.13. For structures not shown, see Chapter 6. 

Coenzyme A is an adenine nucleotide at one end, linked by a S -pyrophosphate to pantothenic acid, a compound that looks rather like a tripeptide, and then to an amino thiol. Here is the structure broken down into its parts. 

Figure 9-22 Structural Formula of Pantothenic Acid. Pantothenic acid R = COOH Panthenol R = CH2OH.

Ynn M, Park CG, Kim JY, Rock CO, Jackowski S, and Park HW (2000) Structural basis for the feedback regulation of Escherichia coli pantothenate kinase by coenzyme A. Journal of Biological Chemistry 275,28093-9. 

Coenzyme A (abbreviated CoA or CoASH, 6) was discovered by Lipmann in the 1940s, and its structure was first reported in 1953 (2, 3). The structure of CoA consists of 3 -phosphoadenosine and pantetheine, linked by a pyrophosphate group (Fig. 1). The pantetheine moiety is derived from pantothenic acid 1, also known as vitamin B5. CoA and its... 

FIGURE 431 Coen -yfne A- The vitamin, pantothenic acid, occurs as part of the structure of coenzyme A,... 

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