Conversion of C14-Palmitic Acid to Glucose

Previous studies on the incorporation of labeled fatty acid carbon atoms into specific glucose carbons have dealt exclusively with short chain acids.Those thus far investigated are acetate, propionate, butyrate, valerate, and octanoate (l-5).The present investigation deals with the conversion of a naturally occurring, long chain fatty acid, palmitic, to urinary glucose in the totally depancreatized dog.The incorporation of palmitic acid-l-C4 and palmitic acid-6-Cl4 into the various carbon atoms of the glucose molecule is reported here.In order to obtain the Cl4 content of individual carbon atoms of glucose, a new procedure for the degradation of this molecule was developed. EXPERIMENTAL Isolation of Glucose from Urine of Diabetic DogAn aliquot of the urine was used to determine its reducing value by the ceric sulfate method of Hassid (6), expressed as glucose.The urine was then clarified by the addition of 50 cc. of a saturated solution of neutral lead acetate, and the resulting precipitate was filtered through Celite.To remove excess lead, 30 cc. of saturated disodium phosphate were added, and the precipitate was once again filtered through Celite.Enough 95 per cent ethyl alcohol was added to the filtrate to double its volume, and the resulting solution was concentrated in vacua to a thick syrup.This syrup was mixed with an equal volume of technical methanol (97 per cent) and warmed on a steam bath until thoroughly mixed.The precipitate' which formed was filtered, and the filtrate was once again concentrated in vacua to a thick syrup.In order to isolate pure glucose from this syrup, the water-insoluble pentaacetyl-a-n-glucose was prepared and hydrolyzed as described below.