ABSTRACT
Anglerfish islet secretory granules have been examined for the presence of an enzyme which could perform C-terminal amidation of glucagon-like peptide II and possibly anglerfish peptide Y. Using [125I]D-Tyr-Val-Gly as substrate, a peptidyl-glycine alpha-amidating monooxygenase (PAM) was detected in islet secretory granule lysates. The enzyme is active between pH 6.0 and 8.5 and exhibits maximal activity near pH 7.0. The islet PAM requires Cu2+, ascorbate, and molecular oxygen for activity. Other divalent metal ions and redox cofactors were tested and found to be inactive in the assay. Even though added Cu2+ and ascorbate are required for detecting islet PAM activity, when these factors were incubated with substrate in the absence of secretory granule lysate, no activity was observed. It was also found that the addition of higher than optimal concentrations of either Cu2+ or ascorbate inhibited amidating activity. The results demonstrate that a PAM is present in secretory granules of anglerfish islet tissue. The characteristics of the islet PAM are similar to those of PAMs identified and characterized in other tissues which produce bioactive C-terminally amidated peptides.
Subject(s)
Cytoplasmic Granules/enzymology , Fishes/physiology , Islets of Langerhans/enzymology , Mixed Function Oxygenases , Multienzyme Complexes , Oxygenases/metabolism , Animals , Ascorbic Acid/physiology , Copper/physiology , Enzyme Activation , Hydrogen-Ion Concentration , Oxidation-Reduction , Oxygen/physiologyABSTRACT
Since 1957, oyster popuulations of the Middle Atlantic coast have been ravaged by a new sporozoan parasite that has been called "MSX." This parasite is identified as a new species of Minchinia that invades oysters through epithelial tissues of gill, palp, water tubes, and, occasionally, of the digestive tract. Multinucleate plasmodia are recognized in fresh and fixed preparations.
