Dephosphorylation of cell-surface phosphoproteins of goat spermatozoa.

Multiple ecto-phosphoproteins of the goat cauda-epididymal intact spermatozoa have been shown to undergo dephosphorylation in vitro by endogenous phosphoprotein phosphatase(s) located on the sperm outer surface. The major ecto-phosphoproteins that are dephosphorylated have molecular masses of 27, 40, 70, 116 and 205 kDa. The cell surface dephosphorylation reaction is not dependent on bivalent metal ions. Mg2+ (5 mM), Mn2+ (5 mM), orthovanadate (200 μΜ) and cAMP (5 μΜ) have no effect on this surface reaction whereas it is inhibited nearly 50% by Co2+ or Zn2+ (1 mM). Spermidine (5 mM), or Ca2+ (1mM) inhibited to a small extent (approx. 25%) the cell surface dephosphorylation of proteins.