CHARACTERIZATION OF PHOSPHOTYROSYL PROTEIN PHOSPHATASE FROM THE HEPATOPANCREAS OF THE SHRIMP PENAEUS-JAPONICUS (CRUSTACEA - DECAPODA)

Phosphotyrosyl protein phosphatase, purified from the hepatopancreas of Panaeus japonicus, is a monomeric enzyme with a relative mass (Mr) of 28,000, as estimated by size-exclusion FPLC on a Superose(TM)12. It has a hydrophobic domain and can be extracted with the detergent CHAPS. The specific activity of the purified enzyme was 9,800 units/mg of protein. The purified enzyme had an isoelectric point less than 4.6, and an optimal pH of 6.5 with either a synthetic peptide or autophosphorylated receptors for insulin as the substrate. The purified phosphotyrosyl protein phosphatase from shrimp hepatopancreas dephosphorylated human and shrimp receptors for insulin and was inactivated by ZnCl2, LiCl, MgCl2, and NaF.