82 METABOLIC PATHWAYS IN MICROORGANISMS 



TABLE 3.5 



Effect of Pyridine Nucleotide on €^^02 Production from 

 Labeled Glucose by Perfused Adult Rat Hearts 



Components per liter of medium: 140 mmoles of NaGl; 5.4 mmoles 

 of KGl, 3 mmoles of CaCl2; 80 //moles of nicotinamide; 900 /imoles 

 of phosphate buffer, pH 7.2; 1.15 mmoles of barbital buffer, pH 7.2. 

 The temperature was 37°. CO2 samples were withdrawn at 30- 

 minute intervals over a 5-hour period. The pyridine nucleotide con- 

 centration was 174 )umoles per liter. 



[specific activity of G^^02 from heart 1 

 ^ . 1 with pyridine nucleotide J 



'specific activity of C^^02 from heart 

 without pyridine nucleotide 



After Jolley, Gheldelin, and Newburgh (29). 



1. The first observations pointing to a synthetic role for 

 the pentose cycle relate to the obvious need for ribose in 

 nucleotide synthesis, and for shikimic acid. Though the 

 biosynthesis of ribose would appear to be most simply 

 effected by the action of G-6-P and 6-PGA dehydrogenases, 

 indications are that this may not be the normal route. 

 Bernstein (65), in a study of the intramolecular distribu- 

 tion of C^^ in nucleotides of chicks fed labeled acetate, 

 glycine, and formate, found it impossible to relate his 

 findings to any oxidative scheme then known, but later 



