Insoluble protein may sometimes show an enzymatic activity

For detection of an enzymatic activity of a target protein, we had better to obtain the protein as a soluble form, whereas it is sometimes difficult. Even when we cannot obtain the target protein as a soluble form, we can still try using it as an insoluble form. Whenever we treat diverse kinds of lysis buffers for solubilizing a protein, some proteins still remain insoluble, which becomes to a hard white pellet that is precipitated on the bottom of the sample collection tube. An insoluble target protein is sometimes completely contained in this pellet. In that case, we can choose an alternative method for using the target protein. The method is to increase the purity of the target protein by a subtraction method that means removing much amount of soluble proteins by treating several kinds of lysis buffers to the pellet. By repeating washing the pellet with many lysis buffers, finally, the content by percentage of the target protein in the remaining pellet significantly increases. When we treat the pellet with an optimal buffer and substrates for its enzymatic activity, if we are fortunate, some enzymatic activities may be observed although the protein does not show a soluble form.