FERMENTS, OR ENZYMF.S 70 



decomposition of maltose into two molecules of glucose there is, how- 

 ever, evidence of synthesis as a result of the acceleration of a reversible 

 reaction. To understand these results we must remember that ordinary 

 dextrose is a mixture of two stereoisomers designated a and /?. When 

 two molecules of a dextrose condense (that is, fuse togther with the 

 loss of a molecule of water) maltose is formed, but when two molecules 

 of /? dextrose condense isomaltose results. There is some controversy 

 as to whether maltase is really responsible for the synthesis of a dextrose 

 molecules to maltose, it being claimed by some that this is accomplished 

 by another enzyme, emulsine. If this were true it would materially 

 minimize the importance of reversible action as a factor in cellular syn- 

 thesis. The latest evidence goes to shoAv, however, that it is maltase 

 and not emulsine that is responsible in the above case (cf. Bayliss). 



Evidence, both direct and indirect, is also steadily accumulating to 

 show that enzymes may accelerate the synthesis of proteins. As pieces 

 of direct evidence we have: (1) the retardation of the digestive action 

 of trypsin, etc., which sets in after the process has gone on for a time, 

 and (2) the recommencement of a digestive process apparently at an 

 end, if the products of the digestion are removed by dialysis or other 

 means. As direct evidence may be cited the* formation of synthetic 

 products when pepsin is added to concentrated solutions of peptone, 

 and the diminution in the number of small molecules, as judged by meas- 

 urements of electrical conductivity, when trypsin is added to the prod- 

 ucts of tryptic digestion of caseinogen. Protamine a simple form of pro- 

 tein has also been found to be produced when trypsin obtained from 

 a mollusc was added to a tryptic digest of the same protamine. The 

 significance of these facts in connection with the metabolism of the 

 amino aids will be evident when we come to study this subject (page 

 598).* 



Specificity of Enzyme Action 



Although in all of the above features of enzyme action there is nothing 

 to contradict the view that they are catalytic agents, there remains one 

 peculiarity which at first sight seems uninterpretable on such a basis. 

 This is with regard to their often remarkable specificity of action. Thus, 

 as we have seen, maltase can hydrolyze maltose alone (which is com- 

 posed of two a-dextrose molecules), but not isomaltose (composed of 

 /^-dextrose). This means that mere difference in the configuration of 

 molecules is sufficient to alter the influence of enzymes on them. Since 

 such differences could not influence that of inorganic catalysts we must 



*We have been unable in this laboratory to demonstrate any synthesis of glycogen when gly- 

 cogenase is added to a hydrolysis mixture of dextritie, maltose and glucose produced by the prolonged 

 action of glycogenase on pure glycogen. 



