You are surprised to observe that the patient's thrombin flows through the cm-cellulose column at ph=6.4 faster than expected based on its pi. confident in your technique, you suspect the patient's thrombin is different from wild-type thrombin. using a different buffer system, you manage to purify some of the patient's thrombin and you submit the purified sample for amino acid sequencing. the sequence analysis shows that the patient's thrombin contains a mutation in the enzyme active site. a lysine residue in the wild type has been mutated to an asparagine in the patient's thrombin. does this mutation explain the anomalous cm-cellulose binding behavior you observed?