I have given the protocol for the cyclodextrin glygosyl
transferase assay:

One ml of appropriately diluted enzyme sample was incubated
at 60 °C for 15 min with 5 ml of 1% (w/v) gelatinized
soluble starch in 50 mM, 7.0-pH Tris–HCl buffer. Reaction
was terminated by boiling the reaction mixture for 3 min
and reaction volume was made to 10 ml with distilled water.
Two ml of above reaction mixture was withdrawn and mixed
with 3 ml of Tris–HCl buffer, 5 ml of 125 mM Na2CO3, and
0.5 ml of phenolphthalein (25 mg phenolphthalein/100 ml
absolute alcohol). Absorbance was measured at 550 nm. The
percent decrease of sample was calculated with respect to
control containing 5 ml of buffer, 5 ml of sodium carbonate
and 0.5 ml of phenolphthalein.



where Acontrol = absorbance of control and Atest =
absorbance of sample.

The amount of β-cyclodextrin (β-CD) produced was estimated
from the standard graph of 0–500 μg/ml β-CD concentration
against % decrease in absorbance. One unit of CGTase was
defined as the amount of enzyme required to produce 1 μm of
β-CD/min.


Please can you suggest me the formula for the defination
given in the last line