360 



Studies on Enzyme Action. X. # — The Nature of Enzymes. 

 By Henry E. Armstrong, F.E.S., and E. Frankland Armstrong. 



(Keceived May 9,— Eead May 23, 1907.) 



[International Catalogue of Scientific Literature. 



Author's title slip : — D. Q. 

 Subject slips : — 



D 1820 Cane sugar, hydrolysis by invertase. 



V Enzymes, nature of (invertase, maltase).] 



The study of the action of enzymes has now reached a stage at which it may 

 be well, in view of their importance as vital agents, to consider what is estab- 

 lished and to call attention to some of the principal issues which remain to be 

 elucidated. 



Specific Activity of Maltase and Umulsin. — As the investigation is extended, 

 the evidence becomes more and more convincing that the action which an 

 enzyme exercises is specific ; in other words, that it is limited to compounds 

 of a particular type — to a greater extent, indeed, than is recognised in 

 earlier communications of this series, which in some few particulars need 

 modification. 



In No. Ill a table is given (p. 520) in which it is indicated (on the authority 

 of Emil Fischer) that maltase hydrolyses a-galactosides as well as a-glucosides 

 and that galactose has a slight retarding effect. At the time when the experi- 

 ments to which the table relates were carried out, no opportunity had been 

 found of verifying Fischer's statement. Subsequently, when experiments 

 were made with methyl-a-galactoside, extracts from both top and bottom 

 yeast proved to be entirely without action. It was then ascertained that the 

 summarised account of Fischer's work which had been consultedf contained 

 an incorrect statement and that the results we had obtained were in harmony 

 with those recorded by Fischer in his original papers.^ 



The slight retardation of the action of maltase by galactose did not appear 

 surprising so long as it was supposed that galactosides were hydrolysed by 

 the enzymes ; when, however, this was found not to be the case, it became 



* Former Communications. — I, 'Chem. Soc. Trans.,' 1903, vol. 88, p. 1305 ; II, ' Eoy. Soc. 

 Proc.,' 1904, vol. 73, p. 500 ; III, ibid., p. 516 ; IV, ibid., p. 526 ; V, ibid., 1904, vol. 74, 

 p. 188 •; VI., ibid., p. 195 ; VII, ibid., 1905, B, vol. 76, p. 592 ; VIII, ibid., p. 600 ; also 

 ibid., 1904, vol. 73, p. 537 ; 1906, B, vol. 78, p. 376. 



t ' Zeit. Phys. Chem.,' 1898, vol. 26, pp. 66 and 69. 



X 'Ber.,' 1894, vol. 27, p. 2987, and 1895, vol. 28, p. 1430. 



