Pantothenic acid, and coenzyme

Various labeled degradation products of pantothenic acid and coenzyme A are known. Both (l- C)-sodium pantothenate (27) and (R)-(l- C)-panthenol are... 

Figure 45-18. Pantothenic acid and coenzyme A. Shows the site of acyiation by fatty acids.

Plesofsky-Vig N and Brambl R (1988) Pantothenic acid and coenzyme A in cellular modification of proteins. Annual Reviews of Nutrition 8, 461-82. 

Jackowski S (1996) Biosynthesis of pantothenic acid and coenzyme A. In Neidhardt FC, Curtiss III R, Ingraham JL, Lin ECC, Low KB, Magasanik B, Reznikoff WS, Riley M, Schaechter M, Umbarger HE (eds) Escherichia coli and Salmonella typhimurium Cellular and Molecular Biology. Vol 1. ASM, Washington DC, p 687... 

Dihydroxyacid dehydratase (E.C. 4.2.1.9) is a ubiquitous enzyme that is involved in the biosynthesis of the branched-chain amino acids (lie, Leu and Val) and of pantothenic acid and coenzyme A. The enzyme catalyzes the elimination of water from 2,3-dihydroxyalkanoic acids (23) to 2-hydroxy-2-alkenoic acids (24), which tautomerize to 2-ketoalkanoic acids (25). The enzyme from spinach has the highest activity towards 2,3-dihydroxy-3-methylbutanoic acid (Val precursor, Scheme 11.5-4) but also accepts other substrates1341. Thus, 2,3-dihydroxybutanoic acid, 3-cyclopropyl-2,3-dihydroxybutanoic add as well as 2,3-dihydroxy-3-methylpentanoic acid are substrates. With the latter substrate a slight preference for (2R,3S)-2,3-dihydroxy-... 

Although pantothenic acid and coenzyme A are undoubtedly important in nutrition in man as well as in animals, no evidence of human pantothenic acid deficiency has been recorded. The wide distribution of pantothenic acid in food may explain this failure to observe deficiency even on restricted diets. The human requirement is unknown but probably is not above 5 mg. dailyIn dogs, the need is similar to that for thiamine and ribofiavin. 

Pantothenic acid (sometimes known as vitamin B, and at one time called vitamin B ) has a central role in energy-yielding metabolism as the functional moiety of coenzyme A and in the biosynthesis of fatty acids as the prosthetic group of acyl carrier protein (section 5.6.1). The structures of pantothenic acid and coenzyme A are shown in Figure 11.26. 

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