12 II. DIGESTION AND ABSORPTION OF FATS 



the decreasing order in percentage hydrolysis of the oils under certain 

 standardized conditions was as follows: peanut, castor, corn, cottonseed, 

 soybean, rape, olive, linseed, neatsfoot, peach-kernel, coconut, whale, fish, 

 and sperm oils. 



Ricinus lipase has an optimum pH of 4.7 to 5.0, 54 depending somewhat 

 upon the buffer employed. During germination, the activity is caused by 

 the production of acid; however, the enzyme exists in the resting seeds, 

 since its action can be demonstrated if the medium is acidified. The 

 optimum temperature is 35°C; at 60°C., the enzyme is largely destroyed, 

 except in the presence of substrate. Under this latter condition, ricinus 

 lipase will show resistance to destruction at temperatures up to 160 o C. 3f ' 

 In contradistinction to steapsin, ricinus lipase is insoluble in water; in 

 fact, in the absence of fat, it is inactivated by water. 58 As in the case of 

 steapsin, castor-bean lipase has been shown to catalyze the synthesis of 

 triglycerides. 59,60 Ricinus lipase may be readily extracted from the ground 

 castor-bean seeds by dilute alkali; methods of purification have been de- 

 scribed by a number of workers. 54,57 - 61 



Lipases have been reported from a number of other plant sources, for 

 example from the seeds of the sunflower (Helianthus annuus), 62 from the 

 greater celandine (Chelidonium majus) , 6S - 64 and from preparations of papain 

 derived from the green fruit of the papaw (Carica papaya). 65 



According to Singer and Hofstee, 66 a lipase could be obtained in soluble 

 form and purified from wheat germ. This enzyme was shown to act on a 

 large number of water-soluble simple esters, as well as on mono- and tri- 

 glycerides, and on Tweens 20 and 40. It is believed that this is a single 

 enzyme; it was shown to be inhibited by all reagents commonly employed 

 for testing — SH-containing enzymes. Calcium ions did not affect its 

 activity. In the presence of excess substrate of either glycerides or simple 

 esters, the enzyme was found to follow a zero order reaction, while inactiva- 

 tion with heat proceeded as a second order reaction. 67 The optimum 

 temperature was found to be 38°C, and the optimum pH (>.8 to 7.4. 67 



58 K. G. Falk, The Chemistry of Enzyme Actions, 2nd ed., Chemical Catalog Co., 

 New York, 1924, p. 137. 



69 H. E. Armstrong and H. W. Gosney, Proc. Roy. Soc. London, B88, 176-189 ( 1914). 

 80 A. Morel and L. Velluz, Bull. soc. chim. biol., 10, 478-488 (1928). 



61 E. Hoyer, Z. physiol. Chem., 50, 414-435 (1900-1907). 



62 F. Traetta-Mosca and F. Milletti, Ann. chim. applicota, IS, 27-288 (1923); Chem. 

 AbsL, 18, 2357 (1924). 



63 K. Bournot, Biochem. Z., 52, 172-205 (1913). 



64 K. Bournot, Biochem. Z., 65, 140-157 (1914). 



65 M. Sandberg and E. Brand, J. Biol. Chem., 64, 59-70 (1925). 



66 T. P. Singer and B. H. J. Hofstee, Arch. Biochem,, 18, 229-243 (1948). 

 87 T. P. Singer and B. H. J. Hofstee, Arch. Biochem., 18, 245-259 (1948). 



