336 GEORGE W. CROSB1E 



fission of the iV-glycoside linkage. Thus cytidine-G-C 14 has been shown by 

 Rose and Schweigart" to be incorporated intact into the deoxycytidine 

 residues of DNA of the rat. This result has been confirmed for a variety of 

 avian 100 and mammalian tissues 101 , 102 and for a cytidineless mutant of 

 Neurospora. m The level at which the sugar interconversion occurs is not 

 clear but Reichard 100 has presented evidence in favor of a reaction at the 

 nucleoside-5'-monophosphate level. 



Together with other deoxynucleotide-5'-triphosphates, dCTP has been 

 shown 94, 104 to be a substrate of an E. coli polymerase enzyme which effects 

 net synthesis of DNA in the presence of primer DNA, Mg ++ , and the other 

 three deoxynucleotide-5'-triphosphates (see Chapter 31). 



A new type of deaminase, deoxycytidine-5'-phosphate deaminase, has 

 been reported recently by Scarano 105 in homogenates and acetone powder 

 extracts of Paracentrotus lividus. The function of this enzyme is not yet 

 clear. 



3. Biosynthesis of 5-Hydroxymethyldeoxycytidine-5'-phosphate 



5-Hydroxymethylcytosine has been identified 106 ' 107 as a constituent of 

 T-even E. coli bacteriophage DNA in which it occurs more or less fully glu- 

 cosylated on the 5-hydroxymethyl group. 108, 109 Bacterial DNA-cytosine is 

 known to serve as a precursor of both viral 5-hydroxymethylcytosine and 

 thymine whereas bacterial thymine cannot be transformed to 5-hydroxy- 

 methylcytosine. 110 The /3-carbon of serine is incorporated into the hydroxy- 

 methyl and methyl groups of 5-hydroxymethylcytosine and thymine, re- 

 spectively. 111 



Flaks and Cohen 112 have recently described a synthesis of 5-hydroxy- 

 methyldeoxycytidine-5'-phosphate from formaldehyde-C 14 and dCMP in 

 the presence of a phosphate buffer extract of alumina-ground T6r + - infected 



9 9 I. A. Rose and B. S. Schvveigert, J. Biol. Chem. 202, 635 (1953). 



00 P. Reichard, Biochim. et Biophys. Acta 27, 434 (1958). 



«' P. M. Roll, H. Weinfeld, and E. Carroll, J. Biol. Chem. 220, 455 (1956). 



02 P. Reichard, Acta Chem. Scand. 11, 11 (1957). 



03 W. S. McNutt, J. Biol. Chem. 233, 189 (1958). 



04 M. J. Bessman, I. R. Lehman, E. S. Simms, and A. Romberg, J. Biol. Chem. 233, 

 171 (1958). 



05 E. Scarano, Biochim. et Biophys. Acta 29, 459 (1958). 



06 S. S. Cohen, Cold Spring Harbor Sy?nposia Quant. Biol. 18, 221 (1953). 



07 G. R. Wyatt and S. S. Cohen, Biochem. J. 55, 774 (1953). 



08 E. Volkin, J. Am. Chem. Soc. 76, 971 (1954). 



09 R. L. Sinsheimer, Proc. Natl. Acad. Sci. U. S. 42, 502 (1956). 



10 L. L. Weed and S. S. Cohen, J. Biol. Chem. 192, 693 (1951). 



1 S. S. Cohen and L. L. Weed, J. Biol. Chem. 209, 789 (1954). 



2 J. G. Flaks and S. S. Cohen, Biochim. et Biophys. Acta 25, 667 (1957). 



