240 



IMMUNO-CATALYSIS 



is based on the ability of the enzyme to decrease the capacity of the 

 mucoid polysaccharide to precipitate acidified (pH 4.2) protein. Two 

 units of hyaluronidase were considered equivalent to one viscosity- 

 reducing unit (see below). Hahnel and Meyer (Meyer, 1947) modi- 

 fied this method so that the ratio of the units determined viscosimet- 

 rically to those measured turbidimetrically varied only from 1.2 

 to 1.4. 



The Viscosity Reducing Method. This method is based on the princi- 

 ple that a solution of a given molecular species flows at a certain speed. 

 As the molecular size increases the rate of flow of the solution de- 

 creases. Splitting of the molecules by enzyme action into smaller molec- 

 ular units increases the rate of flow of the resultant solution. The 

 concentration of the solution, the presence of salts, buffer, and tempera- 

 ture exercise controlling effects on the rate of flow of a given solution. 

 Madinaveitia and Quibell (1940) made use of viscosimetric measure- 

 ments to study the relative activities and degree of purity of various 

 hyaluronidase preparations. Measuring the time required to reach the 

 half-life of the substrate, they observed that enzyme activity runs 

 roughly parallel with the spreading activity of the enzyme in the skin. 

 McClean and Hale (1940, 1941) made extensive use of this method 

 in their study of hyaluronidases. 



Viscosity-Reducing-Unit, (V.R.L/.), was defined as that concentra- 

 tion of enzyme which reduced the viscosity of a standard substrate 

 preparation to a level half-way between its original figure and that of 

 the solvent employed, in 20 minutes. The selection of this period of time 

 was determined by experimental conditions. The following units of 

 activity were found in various enzyme preparations. 



Although a half viscosity level was reached in between one and 10 



Table X 



