- Title
- Mammalian sperm contain a Ca²⁺-sensitive phospholipase C activity that can generate InsP₃ from PIP₂ associated with intracellular organelles
- Creator
- Rice, Anne; Parrington, John; Jones, Keith T.; Swann, Karl
- Relation
- Academic Press Vol. 228, Issue 1, p. 125-135
- Publisher Link
- http://dx.doi.org/10.1006/dbio.2000.9929
- Publisher
- Academic Press
- Resource Type
- journal article
- Date
- 2000
- Description
- We have previously described a phospholipase C (PLC) activity in mammalian sperm cytosolic extracts. Here we have examined the Ca²⁺ dependency of the enzyme, whether there is enough in a single sperm to account for Ca²⁺ release at fertilization, and finally where in the egg is the phosphatidyl 4,5-bisphosphate, the substrate for the enzyme. As for all PLCs examined so far in vitro, we found that the boar sperm PLC activity was Ca²⁺ dependent. Specific activity increased when free Ca²⁺ levels were micromolar. However, even at nanomolar free Ca²⁺ concentration the boar sperm PLC activity was considerable, being two orders of magnitude greater than PLC activities in other tissues. We calculated that PLC activity of a single boar sperm in a mammalian egg is enough to generate 400 nM inositol 1,4,5-trisphosphate (InsP₃) in 1 min, which may be sufficient to account for the observed Ca²⁺ changes in an egg at fertilization. We fractionated sea urchin egg homogenate and examined the ability of boar sperm extract to generate InsP₃ from these fractions. The sperm PLC activity triggered InsP₃ production from a PIP₂-enriched nonmicrosomal egg compartment that contained yolk platelets. We propose that this sperm PLC activity, which is active at nanomolar Ca²⁺ levels and hydrolyzes PIP₂ from intracellular membranes, could be involved in the Ca²⁺ changes observed at fertilization.
- Subject
- phospholipase C; sperm; egg; fertilization; calcium; phosphatidylinositol 4,5-bisphosphate.; inositol 1,4,5-trisphosphate;; sperm factor
- Identifier
- uon:6583
- Identifier
- http://hdl.handle.net/1959.13/804302
- Identifier
- ISSN:0012-1606
- Language
- eng
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