scholarly journals THE COMBINATION OF ENZYME AND SUBSTRATE

1919 ◽  
Vol 2 (2) ◽  
pp. 113-122 ◽  
Author(s):  
John H. Northrop
Keyword(s):  
Quantitative Method ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Albumin Solution ◽  
Hydrogen Ion Concentration ◽  
Egg Albumin ◽  
Insoluble Substrate

1. A quantitative method for the determination of pepsin is described depending on the change in conductivity of a digesting egg albumin solution. 2. The combination of pepsin with an insoluble substrate has been followed by this method. 3. The amount of pepsin removed from solution by a given weight of substrate is independent of the size of the particles of the substrate. 4. There is an optimum zone of hydrogen ion concentration for the combination of enzyme and substrate corresponding to the optimum for digestion. 5. It is suggested that the pepsin combines largely or entirely with the ionized protein.

570. A medium for the simultaneous enumeration and preliminary identification of milk microflora

1955 ◽  
Vol 22 (1) ◽  
pp. 43-47 ◽  
Author(s):  
Kathleen O. Donovan ◽  
J. M. Vincent
Keyword(s):  
Acid Production ◽  
Skim Milk ◽  
Biochemical Properties ◽  
Viable Count ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Pasteurized Milk ◽  
Preliminary Identification

A medium has been developed that permits the viable count of milk bacteria to be combined with the determination of biochemical properties likely to be important in milk itself. This has involved the modification of standard glucose-tryptone skim-milk agar by incorporation of two indicators to detect alkali as well as acid production, substitution of lactose for glucose, and increasing the quantity of skim milk for the detection of proteolysis and casein precipitation. The medium has proved particularly valuable in the study of the thermoduric flora of pasteurized milk. The phenomenon of casein precipitation is, however, less reliably determined than are changes in hydrogen-ion concentration and proteolysis.

Sign in / Sign up

Export Citation Format

Share Document