Enzyme units

Enzyme activity may be described in a number of ways. The commonest is through the initial rate (V₀) of the reaction being catalyzed for example μmol of substrate transformed per minute and μmol min 1). There are also two typical units of enzyme activity the enzyme unit which is denoted by U and the katal denoted by kat. An enzyme unit is which amount of enzyme that will catalyze the transformation of 1 μmol of substrate per minute  at  25^.C  under  finest  conditions  for  that  enzyme.

         Figure: The relationship between product formation and time for an enzyme-catalyzed reaction.

The katal is the accepted SI unit of enzyme activity and is denoted as particularly that catalytic activity which will increase the rate of a reaction through one mole per second in a specified system. It is possible to convert among these variant units of activity using 1 μmol min^-1 =1U =16.67 nanokat.  The word activity  or total activity  refers to the total units of enzyme  in the sample,  while  the specific  activity  is the number  of enzyme  units  per  milligram  of protein that is units  mg^-1. The specific activity is a measure of the purity of an enzyme; in duration the purification of the enzyme its specific activity raise and becomes constant and maximal when the enzyme is pure.