82 ENZYMES 



but the subsequent changes which involve decomposition of the 

 straight chain are not at present understood. Alcohol and 

 lactic acid are possibly steps in the process. Attempts to isolate 

 from various organs an enzyme oxidizing glucose, particularly 

 from the pancreas, muscle, and liver, have led to varying 

 results and much dissention, but it is probable, because of these 

 failures, that no such enzyme exists in quantities sufficient to 

 account for the amount of sugar combustion that is normally 

 accomplished. O. Cohnheim l seems to have explained the 

 failures by his observation that the pancreas produces a sub- 

 stance that activates an inactive glycolytic enzyme in the mus- 

 cles, liver, and probably in other organs. More or less of this 

 activating substance or kinase is present in the blood and 

 organs, determining a certain amount of activity in them when 

 they are removed for experiment, and explaining the varying 

 and inadequate amount of glycolysis often observed. 



The activating substance is presumably an internal secretion 

 from the islands of Langerhans, explaining the relation of these 

 structures to diabetes. Cohnheim believes that the activator 

 unites with the other components of the active enzyme, much 

 as complement and intermediary body unite to form hemolytic 

 and bacteriolytic substances. Although certain features of 

 Cohnheim's work have been contested 2 the most essential 

 features seem to be sufficiently confirmed; namely, that an inter- 

 action between extracts of the pancreas and extracts of muscle 

 or liver produces much more glycolysis than the sum of their 

 independent action would be. 3 



It is quite possible that the important enzyme in glycolysis 

 is not an oxidizing enzyme, but that the ordinary oxidizing 

 enzymes of the cell are able to attack the sugar only after it has 

 first undergone a preliminary splitting by the specific " glyco- 

 lytic" enzyme (O. Baumgarten 4 ). 



LIPASE 



In all cells in which fat is found, and this includes practically 

 all, lipase is probably present in greater or less amount. In 

 the discussion of the reversible action of enzymes on a previous 

 page the most modern conception of fat metabolism has been 

 explained, which considers it to depend upon the existence of 



1 Zeit. f. physiol. Chemie, 1903 (39), 336. 



2 Claus and Embden, Hofmeister's Beitr., 1905 (6), 214. 



3 Simacek, Cent. f. Physiol., 1903 (17), 477, and others have claimed priority, 

 but Cohnheim's work was at least the first to attract general notice. 



* Zeit. f. exp. Path. u. Ther., 1905 (2), 53. 



