THE INHERITANCE OF BIOCHEMICAL CHARACTERISTICS 309 



butyric dehydrogenase. A small part of the acetoacetic acid decarboxylates 

 spontaneously to form acetone. The name ketone bodies is given to the sum 

 of acetoacetic acid, j8-hydroxybutyric acid and acetone. Ketogenesis, 

 although occurring to a slight extent in cells in general, is not accompanied 

 by an accumulation of ketone bodies as takes place in the liver cell. The 

 stationary state in normal liver is characterized by a higher concentration 

 of these substances which then pass into the circulation. The conglome- 

 ration of cells of the liver parenchyma forms the chief site of synthesis of 

 lipides from carbohydrate and the liver cell is responsible for the synthesis 

 of the phosphohpides of blood plasma. 



When we come to consider protein metabolism, the cells of the hepatic 

 parenchyma in mammals are seen to possess important biochemical 

 characteristics. They are the principal site of deamination of amino acids 

 due to their high concentration of glutamic dehydrogenase. This process 

 also occurs in the kidney but the liver, which is also the site of ureogenesis, 

 is distinguished by possessing the system of enzymes which operate the 

 "ornithine cycle". In this cycle glutamic acid, ammonia and CO2 combine 

 to form carbamylglutamate, which in the presence of ATP and Mg++ 

 combines with a further molecule of CO2 and a further molecule of 

 ammonia to give an intermediate whose nature is still unknown. This latter 

 compound reacts with ornithine giving citrulline and regenerating car- 

 bamylglutamic acid. 



HOOC— CH2— CH2— CH— COOH + CO2+NH3 



NH2 



— H2O 

 glutamic acid ^HOOC— CHa— CH^— CH— COOH 



NH 



i 

 carbamylglutamic acid C — NHj 



II 

 O 



HOOC— CH2— CH2— CH— COOH 



NH +NH3 + CO., — — —~> unknown intermediate 



I 

 C— NH, 



page 309, line 20 ..." an intermediate whose nature 

 is still unknown," should be replaced by " an inter- 

 mediate which is carbamyl phosphate ". 



page 309, formulae .... " unknown intermediate " 

 should be replaced by " carbamyl phosphate ". 



-j-caruaniy igiuLaiiin^ av_nj 



Under the influence of an enzyme system that functions in the pre- 

 sence of Mg++ and ATP, the citrulline reacts with aspartic acid forming 



