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Updated: Jul 27, 2025

Defining Substrate Specificities for Lipase and Phospholipase Candidates
Published on: November 23, 2016
Does Phospholipase A
Kiyotaka Matsumura1, Kenji Aketa1
1Akkeshi Marine Biological Station, Faculty of Science, Hokkaido University, Akkeshi, Hokkaido, 088-11, Japan.
Abstract:
We examined whether phospholipase A2 (PLA2 ) is involved in the initiation of the acrosome reaction of sperm of the sea urchin, Strongylocentrotus intermedius, using inhibitors and an activator of this enzyme. Quinacrine and p-bromophenacyl bromide (PBPB) inhibited the egg jelly-induced acrosome reaction at 100 μM, but not the ionomycin-induced one. Depression of egg jelly-induced increase of intracellular free Ca2+ concentration ([Ca2+ ]i ) by these reagents was expected and examined using fura 2. Quinacrine interfered with the flourescence of fura 2, but PBPB was found to depress at concentrations which could inhibit the acrosome reaction. Furthermore, melittin, which is known to stimulate PLA2 , caused a [Ca2+ ]i increase and a formation of acrosomal process-like structure on sperm head. These results suggest that PLA2 participates in the early step(s) of the acrosome reaction of sea urchin sperm.
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