CHEMISTRY OF NUCLEOSIDES AND NUCLEOTIDES 185 



close relationship between CoA and pantetheine (Lactobacillus bulgaricus 

 factor, LBF)-^"' -^^ is established by the conversion of the former into the 

 latter by enzymic digestion. Pantetheine (XLVIII) may also be converted 

 into CoA enzymically in the presence of ATP.-^- 



OH 



HO-CHj-CMes-CH-CO-NH-CHo.CHs-CO-NHCII.CH.-SH 



XLVIII 



Pantetheine (LBF) 



The presence of a pyrophosphate linkage in CoA is indicated by its hy- 

 drolysis with a dinucleotide pyrophosphatase-*^^ • -^^ and supported by its 

 ready conversion into a cyclic phosphate of pantetheine with dilute alka- 

 jj 265, 266 q^j^g formation of cyclic phosphates has been observed under simi- 

 lar circumstances with UDPG (see below) and FAD.-^* The pyrophosphate 

 linkage joins the adenosine residue at position 5' with the pantetheine resi- 

 due at position 4'. This follows from the observation that acid hydrolysates 

 of CoA contain adenosine-5'-phosphate-°^ ■ "^ and pantothenic acid-4'- 

 phosphate (XIJX).-'''^^'' -^'' The formula for CoA is, then, represented 

 byL. 



OH 

 I 

 H.O^PO-CHj-CMerCH-CO-NH-CHj-CHo-CO.H 



XLIX 



Pantothenic acid-4'-phosphate 



POjHj 



-o- 



OH O OH OH OH 



III II I 



CH-CH-CH-CH-CH^-O-P-O-P-O-CHj-CMej-CH-CO-NH-CHj-CH^-CO-NH-CHrCHrSH 



.N^/N. O O 



NHj^ 



N L 



Coenzyme A 



The third phosphate group is a monophosphate, as shown by enzymic 

 hydrolysis with a monophosphatase, and periodate oxidation-^' indicates 

 that it is situated at positions 2' or 3' in the adenosine residue. Since this 

 phosphate is removed by an enzyme which hydrolyzes only 5 nucleotides, 



2«« R. A. McRorie, P. M. Masley, and W. L. Williams, Arch.' Biochem. 27, 471, (1950). 



"1 G. M. Brown, J. A. Craig, and E. E. Snell, Arch. Biochem. 27, 473 (1950). 



"2 R. A. McRorie and W. L. Williams, J. Bacterial. 61, 737 (1951). 



"3 G. D. Novelli, N. O. Kaplan, and F. Lipmann, Federation Proc. 9, 209 (1950) . 



264 G.'D.Nove\U,Phosphoriis Metabolism 1, 4^(1951). 



2" J. Baddiley and E. M. Thain, J. Chem. Soc. 1952, 3783. 



"6 J. Baddiley and E. M. Thain, J. Chem. Soc. 1953, 903. 



«" J. Baddiley and E. M. Thain, /. Chem. Soc. 1951, 3421. 



