b II. DIGESTION AND ABSORPTION OF FATS 



which facilitates contact between the water-soluble enzyme and the water- 

 insoluble substrate. In line with this, Glick and King 26 ' 27 have shown that 

 the activating effect of a compound on lipase is proportional to the lowering 

 in surface tension which it produces. Substances which increase the action 

 of pancreatic lipase were found to inhibit liver esterase to a proportional 

 degree. 27,28 Glick and King interpreted their data as indicative of the 

 fact that two opposing forces operate when a foreign substance is added to a 

 solution containing an enzyme and a substrate. The first effect is to in- 

 hibit the enzyme, either by a physical or a chemical union between the 

 foreign compound and the enzyme, or by a combination with the substrate. 

 The opposing influence is to activate the enzyme by rendering it and the 

 substrate more accessible to each other; this may readily be accomplished 

 by reducing the interfacial tension. Sagar, 29 using a 1 : 100 mixture of olive 

 oil in mineral oil for his tests, noted that the extent of lipolysis was a func- 

 tion of the degree of emulsification. Surface-active emulsifying agents 

 such as monostearyl and distearyl glycerides were superior to bile in pro- 

 moting lipolysis. It was shown that, in the breakdown of neutral fat, 

 active monoglyceride was formed at the oil-water border. It is postulated 

 that, in the biological decomposition of fat, monoglycerides are formed 

 which aid in the emulsification. 



Fodor 30 studied inhibition of the hydrolysis of esters as effected by various 

 propylene glycol mono- and di-esters. The inhibitory effect of isoamyliso- 

 butyrate and of methylhexylcarbinol isobutyrate on the enzymatic hydroly- 

 sis of methylbutyrate was found to be independent of the enzyme concen- 

 tration. 31 The inhibitory effect is markedly increased by prior unification 

 of the inhibitor and the enzyme. On subsequent addition of the substrate, 

 a substrate-inhibitor-enzyme complex is formed which effectively blocks 

 the action of the enzyme on the substrate. This type of inhibition is un- 

 like that brought about by formol, which acts on the enzyme protein itself, 

 or on the enzyme protein-water interface. The action of bile salts on lipase 

 is due to a similar action. Minard 32 also reported that another emulsifying 

 agent, Tween (polyoxyethylene sorbitan) inhibits the action of pancreatic 

 lipase on corn oil. In this case, a less reactive substrate (Tween) inhibits 

 the enzyme action on a more reactive substrate (corn oil), since the Tweens 



26 D. Glick and C. G. King, J. Biol. Chem., 97, 675-684 (1932). 



27 D. Glick and C. G. King, J. Biol. Chem., 94, 497-505 (1931-1932). 



28 D. Glick, and C. G. King, J. Biol. Chem., 95, 477-482 (1932). 



29 C. A. Sagar, Biochem. Z., 321, 44-51 (1950). 



30 P. J. Fodor, Arch. Biochem., 28, 274-280 (1950). 

 81 P. J. Fodor, Arch. Biochem., 36, 311-320 (1952). 



32 F. N. Minard, J. Biol. Chem., 200, 657-660 (1953). 



