24 II. DIGESTION AND ABSORPTION OF FATS 



snake venom and from commercial pancreatin splits purified dipalmitoleyl- 

 L-a-lecithin to a lysolecithin (monopalmitoleyl) and a single molecule of 

 palmitoleic acid. Lecithinase A, called "Phospholipase" by Fairbairn, 147 

 also converts cephalins to lysocephalins. 



A crystalline lecithinase A, prepared from the venom of the rattlesnake 

 (Crotalus terrificus), and a preparation from pancreas, were shown to in- 

 activate succinoxidase in rat liver homogenates and in rat liver mito- 

 chondria. 148 The inactivation is not due to an inhibiting action or to the 

 lytic effect of the lysolecithin. Cytochrome oxidase and succinic dehydro- 

 genase are not appreciably affected by lecithinase A under conditions which 

 completely inactivate succinoxidase. It is suggested that lecithin may be 

 part of a component linking succinic dehydrogenase and cytochrome c. 



(b) Lecithinase B. This enzyme hydrolyzes both fatty acid residues 

 from lecithin, 142 with the formation of glycerylphosphorylcholine. Leci- 

 thinase B has been demonstrated to be a component of rice hulls, 142 of the 

 molds, Aspergillus oryzae (rice mold) 142 and Penicillum. notatum (clay mold). 

 Fairbairn 149 refers to this enzyme as "lysophospholipase." Lecithinase B 

 also acts on phosphatidylethanolamine to produce glycerylphosphoryl- 

 ethanolamine. Lecithinase B is highly specific; it is inactivated by heat at 

 a slightly alkaline reaction, by HCN, and less readily by ions of heavy 

 metals. The optimum pH is at 4.0. 



(c) Lecithinase C. This enzyme splits off choline from lecithin, 142 by 

 rupturing the ester linkage between choline and phosphoric acid. Phos- 

 phatide acid is the compound formed. Hanahan and Chaikoff 150 prepared 

 this enzyme from the carrot; they proved that it was specific for the ester 

 linkage between the nitrogenous base and the phosphoric acid. Maximum 

 activity of this enzyme was in the pH range from 5.2 to 5.9 in a 0.05 M 

 phosphate buffer. It exhibited a high degree of thermostability and was 

 not completely inactivated when exposed to a temperature of 95 °C. for 

 15 minutes. The existence of lecithinase C in carrots has been confirmed 

 by Acker and his co-workers. 151 The activity of this enzyme depends to a 

 considerable degree on the ripeness of the carrots. A similar enzyme is 

 present in germinated wheat, but not in pressed spinach juice. 151 Acker 

 et al. lbl reported that the cleavage of choline proceeded as a first-order 

 reaction. The pH. optimum was found to be 5.8 and the optimum tempera- 



147 D. Fairbairn, /. Biol. Chem., 157, 633-644 (1945). 



148 A. P. Nvgaard and J. B. Sumner, J. Biol. Chem., 200, 723-729 (1953). 



149 D. Fairbairn, /. Biol. Chem., 178, 705-714 (1948). 



150 D. J. Hanahan and I. L. Chaikoff, /. Biol. Chem., 169, 699-705 (1947). 



151 L. Acker, W. Diemair, and R. Jager, Biochem. Z., 822, 471-485 (1952). 



