622 PANTOTHENIC ACID 



COOH 

 COOH CH2 



I I 



CHo CH2 



CH2<- COCoA 



i 



i 



COCoA CH2— COOH 



\ / 

 H2N 



Fig. 10. The mechanism of pyrrole synthesis from succinyl-CoA and glycine. 

 (From Shemin et al.^") 



an acetyl carrier but is more broadly used by the cell as an acyl transfer 

 system. 



Of major importance is the succinyl transfer function of CoA now studied 

 by Green's group^'^ and in Ochoa's laboratory .^^ The principal background 

 of this reaction is the observation that ketoglutarate oxidation, e.g., in 

 heart muscle extracts, is CoA-dependent.-* An ATP-succinate reaction was 

 shown by Kaufman^^ and has recently been also found by Novelli®' to 

 occur in Escherichia coli. Of particular interest appear the indications ob- 

 tained by Shemin'" that succinjd-CoA is likely to be a building stone of the 

 pyrrole ring in the heme molecule. The tentative scheme of condensation 

 of two succinyl-CoA's with glycine is reproduced here from Shemin's paper 

 as an illustration. This scheme, if further substantiated, would confirm on 

 the enzymatic level a previously suspected relationship of pantothenic acid 

 to erythrocyte metabolism.'^ 



3. Fat and Steroid Synthesis 



The identification of acetate by isotope analysis as a precursor of fatty 

 acid, cholesterol, and steroid hormones^^ indicated that the initial con- 

 densation reactions leading to these syntheses should belong to the acetyl 



" A. Kornberg and W. E. Pricer, Jr., Federation Proc. 11, 242 (1952). 



5* H. A. Barker in Phosphorus Metabolism, Vol. I, p. 204. Johns Hopkins Press, 



Baltimore, 1951. 

 ^^ E. P. Kennedy, cf. in Phosphorus Metabolism, Vol. I, p. 240. Johns Hopkins 



Press, Baltimore, 1951. 

 8« V. H. Cheldelin, A. P. Nygaard, O. M. Hale, and T. E. King, /. Am. Chem. Soc. 



73, 5004 (1951). 

 " H. P. Klein, Federation Proc. 10, 209 (1951). 



98 H. P. Klein and F. Lipmann, /. Biol. Chem. 203, 95 (1953); H. P. Klein and F. 

 Lipmann, ./. Biol. Chem. 203, 101 (1953). 



99 R. J. Williams, R. E. Eakin, E. Beerstecher, Jr., and W. Shieve, The Biochemistry 

 of the B Vitamins, p. 423. Reinhold Publishing Corp., New York, 1950. 



