66 II. DIGESTION AND ABSORPTION OF FATS 



The action of chlorophyllase in producing the so-called "crystalline chlo- 

 rophylls" (chlorophyllides a and b), was first explained by Willstatter and 

 Stoll. 383 The method of hydrolysis in hot water was discovered by B. E. 

 Lesley and J. W. Shumate (see Weast and MacKinney). 382 Mayer 384 re- 

 ported that, in a 66% acetone solution, chlorophyllase had an optimum 

 temperature of 25°C. and an optimum pH of 6.0 to 6.2. This is the same 

 optimal temperature as that reported for an 80% alcohol solution. The 

 acetone concentrations could be varied between 40 and 70% with no change 

 in activity, but the limits for optimum activity with ethyl alcohol were 

 only from 70 to 80%. Although the optimum temperature for aqueous 

 solutions of chlorophyllase is 75 °C, the enzyme may act equally effectively 

 at 50°C. when the leaf has been previously frozen. Apparently the acces- 

 sibility of the substrate is of prime importance in determining the extent 

 of hydrolysis. 



According to Mayer, 384 chlorophyll-a is split by chlorophyllase at a rate 

 1.8 times that of chlorophyll-6. This worker reported that great variations 

 in chlorophyllase obtained at different seasons; KCN was shown to have 

 little effect on this esterase. Weast and MacKinney 382 likewise confirmed 

 the fact that potassium cyanide was without effect on chlorophyllase; 

 moreover, sodium fluoride caused only a slight change in activity, but mer- 

 curic nitrate (Hg(N0 3 )2) in 0.1% concentration produced a complete in- 

 activation of the Scrophularia enzyme in alcohol. Finally, these latter 

 workers demonstrated that the chlorophyllase activity of several species 

 of green plants varied widely according to the solvent employed. The 

 rate of hydrolysis in prickly-seed spinach (Spinacia oleracea), was highest 

 in water, but there was little activity in acetone or alcohol. In the case of 

 California figwort (Scrophularia calif ornica), a very high activity was ob- 

 served in alcohol but none in water. No chlorophyllase could be demon- 

 strated in the mid oat (Avena fatua). These data are summarized in 

 Table 7. 



It has recently been shown that chlorophyllase also acts to hydrolyze 

 bacteriophaeophytin-a to bacteriophaeophorbid-o. 385,386 The former com- 

 pound is obtained from bacteriochlorophyll-a by treatment with acid 386 ; 

 in the presence of methanol, bacteriomethylphaeophorbid-a, C36H 3 8N 4 6 ± 

 2H, is formed. 387 Bacteriochlorophyll-a, the commoner of the green pig- 



383 R. Willstatter and A. Stoll, Untersuchungen iiber Chlorophyll, Springer, Berlin, 

 1913. 



384 H. Mayer, Z. wissensch. Biol, Abt. E. Planta, 11, 294-330 (1930). 



385 H. Fischer and K. Bauer, Ann., 523, 235-284 (1936). 



386 E. Schneider, Ber. deut. botan. Ges., 52, 96-100 (1934). 



387 H. Fischer and J. Hasenkamp, Ann., 515, 148-164 (1934). 



