METABOLISM OF THE CANCER CELL 



12 



Inorganic phosphate -^ 



+ ATP, GTP, CTP, UTP 



Glycolysis and 

 oxidation 



Nucleotide^ 

 precursors 



A 



Inorganic phosphate 



+ 

 — ^k. Fiuiction 



.ADP, GDP, CDP. UDP 



\ 



Ribonucleic acids 



2H 



Specific metabolic reductions 



Reduced c\ lochronie c H,0 



n 



'\ 



Oxidized c\lochrome c 



O, 



Pyrimidine 

 deoxvribotide formation 



Specific metabolic reductions 



Fig. I . Relation between respiratory balance and DNA or RNA synthesis. * Enzyme Xj 

 is speculative, the other enzymes are known to exist. (From Potter, 1956). 



These speculative charts ilhistrate how alterations in respiratory enzyme balance 

 may shift the metabolism in the direction of deoxyribonucleic acid production, 

 ribonucleic acid formation or towards other metabolic functions. 



(c) Citric cycle 



The excellent compilations of Greenstein (1954, 1956) provide a most com- 

 prehensive review of the concentrations and activities of the components and 

 enzymes involved in the oxidation of pyruvate. It is evident from a qualitative 

 standpoint that tumors do contain all of the known enzymes involved in the citric 

 cycle. Quantitatively there are wide ranges in the activities of these enzymes in 

 various normal tissues. Generally, the activities of these enzymes in tumors ap- 

 proximate the lowest normal values, the tumors showing a uniform behavior in 

 this respect. Pyruvate, oxalacetate, citrate and ketoglutarate, succinate, fumarate 

 and malate are readily oxidized by tumor homogenates fortified with DPN 

 (Weinhouse, 1951, 1955; Wenner and Weinhouse, 1953). Weinhouse (1955) 



