220 IMMUNO-CATALYSIS 



sequent treatment with hydrogen sulfide. Only small loss of activity 

 ensued on acetylation with ketene. That free sulfhydryl groups are 

 associated with the activity of jS-amylase are shown by the following 

 tests: (a) positive nitroprusside test for free -SH group; (b) the in- 

 activation by dilute iodine is reactivated by hydrogen sulfide; (c) 

 significant reactivation by hydrogen sulfide when the loss of activity is 

 caused by the combined action of ferricyanide and cupric ions; (d) the 

 inactivation of /3-amylase by aryl-mercuric compounds and disappear- 

 ance of the nitroprusside reaction for free -SH groups was completely 

 or largely reversed by subsequent treatment with hydrogen sulfide or 

 with cysteine; and (e) irreversible inactivation of ^-amylase by iodo- 

 acetamide which is known to enter into irreversible combination with 

 -SH groups. This combination, as expected, was not reversed by 

 cysteine. 



a. Antibody Against Malt Amylase. Liiers and Albrecht (1926) 

 carried out their experiments taking into consideration the objections 

 raised by Bayliss regarding the existence of anti-enzyme antibodies. 

 The question of H"^ concentration, and the question of adsorption of 

 the enzyme on non-specific precipitates were in particular studied. The 

 reaction systems used were well buffered and controlled, and there- 

 fore there was no question of changes in H+ being responsible for 

 the abolition of amylase activity in the presence of homologous im- 

 mune serum. The amylase activity studied in the presence and ab- 

 sence of egg-albumin-anti-egg albumin precipitates was likewise shown 

 to be identical; therefore, there was no diminution of amylase activity 

 as a result of adsorption of the enzyme on non-specific precipitates. 



Experimental. Amylase was prepared from malt according to the 

 method of Sherman and Schlesinger (1913, 1915). Various amylase 

 preparations were studied. One part of these preparations hydrolyzed 

 a 3 per cent solution of starch producing 250 to 380 times as much 

 maltose as the weight of the enzyme used. 



Acetate buffer of pH 5 (16.4 ml. of 0.5 N acetate buffer in 100 ml. 

 reaction mixture) was used to regulate the H+ concentration. In all 

 the experiments, the amount of amylase used was from 0.0025 g. to 

 0.005 g. of amylase by dry weight which was capable of hydrolyzing 

 100 ml. of 3 per cent starch solution at pH 5 and 20°C. during a pe- 

 riod of 30 minutes. To determine the degree of hydrolysis of starch, 

 the cuprous oxide resulting from the reduction of copper reagent by 



