TRIGLYCERIDES AND FATTY ACIDS 119 



a phosphomonoesterase, but rather by a phosphorylase requiring adenosine 

 or adenylic acid as a coenzyme. It had been shown earUer that vitamins B, 

 nicotinamide, pyridoxine, and pantothenic acid act as coenzymes. -^^ 



b'. The Distribution of 9,10-Dehydrogenase: In addition to the liver 

 and muscle as sources of dehydrogenases,^^^'^^^ the small intestine (rats),^^^ 

 bile, pancreas,-*^ and kidneys, -^^ have also been reported to be sites of origin. 

 Annau et al. noted their presence in the liver, but they found that only 

 lecithin, palmitic acid, and stearic acid could be dehydrogenated. 



Shapiro and Wertheimer,-^^ Quagliariello alone^° and with Scoz-^^ called 

 attention to the presence of a fatty acid dehydrogenase in adipose tissue 

 itself. The enzyme requires the presence of a coenzyme, adenylic acid, and 

 of inorganic phosphate. It has an optimum pH of 8.0 The highest activity 

 is fomid in relation to natural, long-chain fatty acids; its effectiveness de- 

 creases with diminishing chahi length. In addition to fatty acids, this 

 enzyme attacks phospholipids and succinic acid, but not neutral fat. The 

 enzyme is also present in liver, heart, muscle, and testes. The action of the 

 dehydrogenase is not decreased by monoiodoacetate, sodium fluoride, 

 phlorhizin, maleic acid, pyrophosphate, or benzoate at fairly high concen- 

 trations, but it is inhibited by oxygen. 



{3) Pathways of Fatly Acid Oxidation 



Crandall and co-workers^^" suggested the existence of alternative path- 

 ways for fat oxidation, one by means of acetone body production in the 

 liver, and a second one which does not involve ketogenesis. It is assumed 

 that ketogenesis is a mechanism which supphes the tissues with substances 

 which can be used as a partial replacement for glucose in metabohsm, and 

 which therefore conserves the carbohydrate reserve and decreases the 

 need for gluconeogenesis. Barnes and collaborators^^^ have independently 

 arrived at essentially the same conclusion by studying the ketone body 

 utilization in animals in a state of ketosis produced by pancreatic diabetes 

 or by phlorhizin. 



However, in view of the more recent demonstration by the use of iso- 



^^ J. Champougny and E. LeBreton, Compt. rend. soc. bioL, I4I, 43-45 (1947). 



2^5 H. D. Cremer, Z. physiol. Chem., 263, 240-242 (1940). 



"8 H. Tangl and N. Berend, Biochem. Z., 232, 181-188 (1931). 



^' F. P. Mazza, Boll. soc. ital. biol. sper., 9, 298-299 (1934). 



25^ B. Shapiro and E. Wertheimer, Biochem. J., 37, 102-104 (1943). 



2" G. Quagliariello and G. Scoz, Arch. set. biol. (Italy), 17, 513-529; 530-545 (1932). 



^'^ L. A. Crandall, Jr., H. B. Ivy, and G. I. Ehni, Am. J. Physiol, 131, 10-17 (1940); 

 J. Biol. Chem., 138, 123-128 (1941). 



2«' R. H. Barnes, D. R. Drurv, P. O. Greeley, and A. N. Wick, Am. J. Physiol, 130. 

 144-150 (1940). 



