CDNTKNTS xix 



[\. I'lie Question of the Conversion of Fat to Carbohydrate (C<tii limied) 



(4) The Importance of Insulin 230 



(5) Experimental Data from Isolated Organs 230 



a. Fat Change and Carbohydrate Content 230 



b. Fat Change and Respiratory Quotient 231 



5. Resume of Current Hypotheses Regarding the Fat — > Carbohydrate 



Conversion 232 



V. The Oxidation and Metabolism of Phospholipids and Their Hydrol- 

 ysis Products 235 



1. Hydrolysis of Phospholipids 235 



2. The Degradation of Phospholipids by Means Other Than by Hj'drolysis 238 



3. The Oxidation and Metabolism of Hydrolysis Products of Phospholipids 239 



(1) Choline 239 



a. Introduction 239 



b. Choline Oxidase 239 



(a) Distribution of Choline Oxidase 239 



(b) Chemical Nature of Choline Oxidase 240 



(c) Mechanism of Action of ChoUne Oxidase 241 



(d) Factors Altering the Activity or Concentration of Choline 



Oxidase 242 



c. The Course of Choline Metabolism 244 



d. Choline as a Source of Glycine 245 



(2) Ethanolamine 245 



a. Introduction 245 



b. Sources of Ethanolamine in the Animal Body 246 



c. Degradation of Ethanolamine in the Animal Body 246 



(3) Serine 247 



(4) Sphingosine 248 



4. The Effect of Deficiency of the Phospholipids 249 



(1) The Effect of Phospholipid Deficiency in General 249 



(2) The Effect of Choline Deficiency. . . / 250 



VI. The Role of Acetic Acid, Formic Acid, and Propionic Acid in the 



Intermediary Metabolism of Fats 253 



1 . Acetic Acid and Acetate 253 



( 1 ) The Occurrence of Acetic Acid in the Animal Body 254 



(2) Sources of Acetic Acid in the Animal Body 257 



a. Formation from Even-Chain Fatty Acids 257 



b. Formation from Odd-Chain Fatty Acids 258 



c. Formation from Pyruvate 259 



d. Formation from Amino Acids 261 



(3) Acetylation Reactions in the Animal Body 262 



a. Acetylation of Amino Acids and Amides 264 



b. Formation of Mercapturic Acid 266 



c. Acetylation of Choline 267 



(4) Metabolic Reactions Involving Acetate 267 



