228 



given, and that this must consist in different velocities of attack. 



Most of these reactions appear intrinsically to be true reversible 

 or semi-reversible reactions *) : thus glycose is changed by maltase 

 into maltose (or rather into iso-maltose) 2 ) in this way; kefir-lactase 

 acting on a mixture of glycose and galactose, produces iso-lactose, etc. 

 The same is true for the action of lipase, of emulsine, and of a 

 number of other animal or vegetable enzymes. 



The close analogy with the effect of yeasts on sugars, formerly 

 stated by Fischer 3 ), is evident; thus from i-glycose the /^-handed 

 component may for instance be obtained by means of yeast, because 

 yeast attacks the d-glucose, while during the same time it does not 

 attack the l-glucose, or only to an unappreciable extent; in the 

 same way as in Pasteur's original experiments the d-ammonium- 

 tartrate was attacked almost exclusively by Penicillium glaucum 

 during warm weather, but not the laevogyratory salt. It happens 

 in many cases, that if a substance can be fermented both by emulsine 

 and by invertase, the behaviour of both enzymes towards the antipo- 

 des is just opposite. Whether this may be considered to be a general 

 rule, is not certain. Fischer stated that all enzymes fermenting 

 maltose, act in an analogous way on a-glucosides 4 ) 



Of course, the disadvantage of this method of fission is, that half 

 of the material is destroyed, only one of the optically active com- 

 ponents being preserved. Moreover, the substances must be such, 

 that living organisms can grow in their solutions; because of the 

 exclusively selective action, it is often a difficult matter to find the 

 right organism to effect the desired separation. 



11. Although in the next chapter we shall return to the details 

 of the method, a few words must again be said on a fission-method, 

 as used by some investigators, which method is founded on the 



*) Literature on the reversibility of enzyme-action; A. Croft Hill, Journ. Chem. 

 Soc, London, 73, 634, (1898) ; 83, 578, (1903) ; J. H. Kastle and A. S. Loevenhart, 

 Amer. Chem. Journal, 24, 491, (1900); M. Hanriot, Compt. rend, de 1'Acad. d. 

 Sc. Paris, 132, 212, (1901); H. Pottevin, Compt. rend., 136, 767, (1903); E. Bour- 

 quelot and M. Bridel, Ann. de Chim. et Phys., 28, 145, (1913); W. M. Bayliss, 

 Journ. Physiol., 36, 221, (1907); 43, 455, (1912); 46, 236, (1913). 



2 ) E. Fischer, Ber. d. d. Chem. Ges., 32, 3617, (1899) ; Zeits. f. physiol. Chemie, 

 26, 60, (1898); E. Fischer and E. F. Armstrong, Ber. d. d. Chem. Ges., 35, 3144, 

 (1902). 



3) E. Fischer, Ber. d. d. Chem. Ges., 23, 2620, (1890). 



4) E. Fischer, Zeits. f. physiol. Chemie, 26, 69, 79, (1898). 



