A mutation in enzyme X was found to associated with a genetic disease. You have the following information. a. X is single polypeptide for MW 50,000.
b. Non-denaturing electrophoretic analysis of mutant and normal X shows that the mutant behaves as if it has one extra positive charge.
c. The N-terminal amino acid is Thr and the C-terminal amino acids is Asn.
d. Both the mutant and normal X give exactly the same number of peptides when treated with trypsin (cleaves at positively charged residues).
e. Chemical modification with His specific reagents shows that both mutant and normal X have the same number of His residues.

Of the following amino acids, Lys, lle, Asp, His is the amino acid that has changed, and is the most likely the new amino acid in the mutant.