ANTI-ENZYME IMMUNITY 219 



greater for linkages at a distance from end-groups, a- Amylase and 

 malt-amylase free from maltase (a-glucosidase) form glucose directly 

 from dextrin, showing that glucose is formed not only from starch 

 but also from short chain saccharides (4 to 6 glucose units) with 

 maltose linkages (a-dextrins). 



Amylose, having solely unbranched chains of glucose residues, is 

 hydrolyzed by ^S-amylase until the whole molecule is degraded to 

 maltose units (for a general review of the subject see, Meyer, 1943; 

 Hassid, 1945). 



/?- Amylase has been obtained in crystalline form from sweet potatoes. 

 This crystalline protein (17.48 per cent nitrogen) was free from 

 a-amylase activity (Balls, Thomson and Walden, 1946). a- Amylase has 

 been obtained from the pancreas likewise in crystalline form (Meyer, 

 Fischer and Bernfeld, 1945). A molecular weight of less than 20,000 

 by the diffusion method has been calculated. 



a- Amylase. Little and Caldwell (1942, 1943) sought to determine 

 the nature of the active groups in pancreatic a-amylase. Primary amino, 

 sulfhydryl and phenolic tyrosine groups were the objects of their study 

 as being possibly responsible for the activity of enzyme protein. Using 

 ketene for acetylation, they established that the primary amino groups 

 of the enzyme protein are essential to the activities of amylase. No 

 evidence was found for the presence of free -SH groups in the active 

 enzyme or for their importance to its activities. Amylase was not easily 

 oxidized or reduced. lodoacetic acid, which is specific for the sulfhydryl 

 group of proteins, failed to affect the activity of the enzyme. Phenolic 

 groups of tyrosine were of little, if any, importance to the activities of 

 the amylase. Amylase was inactivated by formaldehyde, phenylisocy- 

 anate and nitrous acid, which are known to react with primary amino 

 groups. Schwimmer and Balls (1949) have obtained a-amylase of ger- 

 minated barley (malt) in crystalline hexagonal prism. From osmotic 

 pressure data a molecular weight of about 59,500 was calculated. One 

 molecule of enzyme was found to hydrolyze 19,000 glycosidic bonds 

 per minute. It appears that crystalline preparations require two 

 calciums per molecule of a-amylase. 



^-Amylase. Unlike a-amylase, the activity of i8-amylase from barley 

 and malted barley was related to free -SH and phenolic tyrosine groups 

 (Weill and Caldwell, 1945). Inactivation by nitrous acid was com- 

 pletely reversed in the early stages of the reaction at least, by sub- 



