ENZYMES CONCERNED WITH DIGESTION OF LIPIDS 21 



enzyme in the blood, Nomura 126 denied that cholesterol esters are hydro- 

 lyzed in the blood ; however, the latter worker did demonstrate that such a 

 change could be mediated by a number of tissues other than blood. Shope 127 

 reported that cholesterol is hydrolyzed in the blood, but Sperry 128 questions 

 the results, since adequate control tests for a concomitant synthetic action 

 were not made. However, Sperry and Brand 125 later demonstrated that 

 only the hydrolytic activity on the part of cholesterol esterase could occur 

 in the blood; the particular effect which was noted was found to depend 

 upon the experimental conditions. 



In view of the demonstration of cholesterol esterase in pancreatic juice, 120 

 it is only natural that one would expect to find it in the pancreas itself. 

 Yamamoto et a/,. 129 demonstrated this enzyme in commercial pancreatin, 

 while Fodor 130 reported the presence of both the hydrolytic and the syn- 

 thetic cholesterol esterases in hog pancreas homogenates. Optimum pH 

 values for the hydrolytic and synthetic activities were 6.3 and 5.2, respec- 

 tively. Both types of cholesterol esterases have likewise been demon- 

 strated by Swell, Byron, and Treadwell 131 in rat intestinal mucosa. Opti- 

 mum activities of the hydrolytic and synthetic intestinal cholesterol ester- 

 ases were given for pH 6.5 and 6.2, respectively. Since the amount of 

 these enzymes in the mucosa is markedly reduced in depancreatized rats, it 

 is suggested 131 that the pancreas is the major or sole source of the cholesterol 

 esterase in the mucosa. 



The presence of a cholesterol ester-hydrolyzing enzyme has been reported 

 in a number of tissues of the guinea pig, by Shope 127 ; in addition to the 

 liver, kidney and muscle were reported to contain the highest amounts. 

 Klein 124 found that 70 to 85% of cholesterol esters were hydrolyzed in 15 

 hours at a pH of 5.3 by preparations of the liver, spleen, kidney, adrenal, 

 and intestinal mucosa. At this pH, the synthetic phase of the reaction 

 would be almost completely inhibited. 



Nieft 132 has shown that cholesterol esterase (which causes hydrolysis of 

 cholesterol esters), prepared from intestinal mucosa of the rat, consists of 

 two factors. The first of these is a globulin type protein which is heat- 

 labile and is precipitated by 50% saturation with ammonium sulfate. 



126 T. Nomura, Tohoku J. Exptl. Med., 4, 677-684 (1924). 



127 R. E. Shope, J. Biol. Chem., SO, 127-132 (1928). 



128 W. M. Sperry, J. Biol. Chem., Ill, 467-478 (1935); 113, 599-606 ( 1936). 



129 R. S. Yamamoto, N. P. Goldstein, and C. R. Treadwell, ./. Biol. Chem., ISO, 615-621 

 (1949). 



130 P. J. Fodor, Arch. Biochem., 26, 331-336 ( 1950). 



131 L. Swell, J. E. Bvron, and C. R. Treadwell, ./. Biol. Chem., 1S6, 543-548 (1950). 



132 M. L. Nieft, J. Biol. Chem., 177, 151-156 (1949). 



