Tyrosine specific esterase activity in the epidermal secretions from the Arabian Gulf catfish, Arius bilineatus (valenciennes)

1. 1. The shock-induced epidermal secretions from the Arabian Gulf catfish, Arius bilineatus, contain two classes of esterase activities. 2. 2. One class of esterase activity catalyzes hydrolysis of the general esterase substrate, p-nitrophenyl acetate, and the second is specific of esters for tyrosine. 3. 3. The tyrosine specific esterase has been purified 322-fold and its physical and enzymic properties have been studied. 4. 4. The tyrosine specific esterase is a serine-type esterase with a molecular mass between 70,000 and 100,000 daltons. 5. 5. This enzyme has no measurable amidase activity, though tyrosine amides are effective inhibitors of its esterase activity.