NOVEMBEE 4, 1921] 



SCIENCE 



443 



growth but does not check the action of the enzyme. 



(3) The following method is suggested: Boiled 

 cream of high fat cont«nt is used as substrate. 

 Cane sugar is added in sufficient quantity to form 

 a saturated solution with all the water present. 

 After addition of the enzyme, the mixture is titrated 



.at the beginning and end of a digestion period. 



(4) It is proved that milk normally contains lipase. 



(5) Lipase doubtless is a factor in the development 

 of rancidity in seed oils, butter and cheese. (6) 

 Direct proof is offered that sweetened condensed 

 milk becomes rancid on account of an admixture 

 of raw mUk, the lipase therein producing the 

 phenomenon. 



A quantitative method for the determination of 

 peroxidase in millc: Frank E. Eice, and T. Han- 

 ZAWA. (1) The method of Bach and Chodati is 

 modified for application to milk. It depends upon 

 the oxidation of pyrogallol to insoluble purpuro- 

 gallein with hydrogen peroxide, the reaction being 

 catalyzed by peroxidase. (2) The milligrams of 

 purpuTOgallein obtained per 10 c.c. of milk is taken 

 as the " peroxidase number." (3) Since several 

 days are necessary for the attainment of equi- 

 librium air must be excluded from the reaction. (4) 

 The dependence of the peroxidase number on the 

 amount of peroxidase present was proved by making 

 determinations on various mixtures of raw and 

 boiled milk. 



Effects of certain antiseptics upon the activity of 

 amylases: H. C. Sherman and Marguerite Wat- 

 man. The influence of toluene, formaldehyde and 

 copper sulphate upon amylases of both animal and 

 vegetable origin was studied. Toluene had very 

 little influence upon the activities of the amylases 

 either in their natural or purified condition. For- 

 maldehyde even' in small amounts (0.00006 molar 

 and less) was found distinctly injurious to all of 

 the amylases studied, viz., commercial panereatin, 

 purified pancreatic amylase, saliva, malt extract, 

 purified malt amylase, commercial takadiastase, and 

 the purified amylase of Aspergillus orysos. Taka- 

 diastase was the least, and purified pancreatic 

 amylase was the most, affected. All of these 

 enzymes were also found to be very sensitive to 

 copper sulfate. The percentage loss of enzyme 

 activity under the influence of formaldehyde or cop- 

 per was determined by the concentration of the 

 antiseptic in the solution and not by the ratio of 

 antiseptic to enzyme or to substrate. The results 

 as a whole, in addition to their bearing upon the 

 problem of quantitative distinction between organ- 



iBer. d. d. Chem. Ges., 37 (1904), 1342. 



ized and unorganized ferment action, are of inter- 

 est in that they afford a new indication of the pro- 

 tein nature of these typical enzymes. 



The influence of certain amino acids upon the 

 emymio hydrolysis of starch: H. C. Sherman and 

 Florence Walker. Addition of glycine, alanine, 

 pheylalanine or tyrosine caused an undoubted in- 

 crease in the rate of hydrolysis of starch by puri- 

 fied pancreatic amylase, commercial panereatin, 

 saliva, or purified malt amylase. Less marked re- 

 sults were obtained with the less sensitive enzyme 

 materials malt extract, takadiastase, and an Asper- 

 gillus amylase product prepared in the laboratory 

 from takadiastase. Each of the four amino acids 

 here studied, as well as aspartic acid and aspara- 

 gine previously reported, showed a similar favor- 

 able influence upon the enzymic hydrolysis of the 

 starch. The addition of a mixture of two of these 

 amino acids produced no greater effect than would 

 result from the same concentration of one of them. 

 In these experiments the favorable effect of the 

 added amino acid was not due to any influence upon 

 hydrogen-ion concentration nor to combination of 

 the amino acid with the product of the enzymic 

 reaction. On the other hand, it is shovm that the 

 addition of one of these amino acids is a very 

 effective means of protecting the enzyme from the 

 deleterious effect of copper sulfate and may even 

 serve to restore to full activity an enzyme which 

 has been partially inactivated by copper. 



A study of the influence of arginine, histidine, 

 tryptopliane and cystine upon the hydrolysis of 

 starch by purified pancreatic amylase: H. C. Sher- 

 man and Mart L. Caldwell. Arginine, histidine, 

 tryptophane and cystine were tested as to their in- 

 fluence upon the amyloclastie activity of a purified 

 preparation of pancreatic amylase and it was found 

 that arginine and cystine have a favorable influ- 

 ence, while histidine and tryptophane do not. Since 

 the conditions of the experiments were carefully 

 controlled and were uniformly favorable as to 

 hydrogen-ion concentration and kinds and amounts 

 of salts present, the differences in results are due 

 to the specific effects of the individual amino acids. 

 That histidine and tryptophane should have a dif- 

 ferent influence from all the other amino acids 

 studied in this and the preceding investigations may 

 be due either to their heterocyclic structure or to 

 their position in the protein complex which doubt- 

 less constitutes either the enzyme molecule itself or 

 an essential part of it, or to both. The influence of 

 chemical structure of added substances upon their 

 effects on enzyme action is being studied further. 



