Abstract
A method for determining the isoamylase activity is devised. A properly diluted enzyme solution is allowed to act at 20°C on a 1% solution of glutinous-rice starch buffered to pH 6.2. After 24 hours, 0.2cc of then reaction mixture is mixed with 2cc of 0.01 N I2 solution, and diluted to 25cc. Optical density (E) of the solu-tion at 620mμ is read in a Pulfrich photometer, using a 1-cm cell. The increment of E at 620mμ is proportional to enzyme activity within certain ranges. The amount of enzyme is expressed in the “isoamylase unit”, i.e., an increase of E 0.200 being taken as 10 units.
A pH-activity curve is given for yeast isoamylase, which shows a sharp maximum at pH 6.2.
