The specific activity of an enzyme would be reported in which of the following units of measure?
|A||Micromoles per minute|
|B||Milligrams per micromole|
|C||Millimoles per liter|
|D||Units of activity per milligram of protein|
a. Substrate concentrations are usually expressed in terms of molarity, e.g., M = moles per liter, mM = millimoles per liter,= micromoles per liter.
b. Km, the Michaelis constant, is expressed in terms of substrate concentration. Each unit of enzyme activity is described as the amount of enzyme that converts a specific amount of substrate to a product within a given time. The standard units of activity are micromoles of substrate per minute.
c. Specific activity relates the units of enzyme activity to the amount of protein present in the reaction, expressed as units of enzyme activity per milligram of protein.
d. If the enzyme is pure (no proteins except the assayed enzyme are present), then the specific activity is maxi mal and constant for that particular enzyme (units of activity per milligram of enzyme). The specific activity is a useful measure of enzyme purity that should increase during enzyme purification.