What is the protein concentration of proteinase K (molecular biology grade)?

The protein concentration of proteinase K is 20 mg/ml, as determined by UV absorption at 280 nm. Its unit activity is 800 U/ml. Protein concentration is determined by dividing the digest solution absorbance by the calculated epsilon (M) (280). The absorptivity of a native protein is then calculated by dividing the absorbance of the intact protein solution by the concentration value calculated for the digest solution.