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Effect of modulators on prostasome membrane‐bound ATPase in human seminal plasma
Author(s) -
RONQUIST G.
Publication year - 1987
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1111/j.1365-2362.1987.tb01241.x
Subject(s) - atpase , microbiology and biotechnology , chemistry , membrane , biophysics , human plasma , plasma , biology , biochemistry , enzyme , physics , chromatography , quantum mechanics
. The Mg 2+ ‐ and Ca 2+ ‐dependent ATPase system in human seminal fluid is linked to membranes encasing small organelles denoted ‘prostasomes’. This activity was completely pelleted after ultracentrifugation at 105 000 x g , provided the seminal plasma was diluted 1:10. On the contrary, prostatic acid phosphatase activity remained in the supernatant and was inhibited to about 75% by tartrate (0·5 mmol l ‐1 ) contrasting with the ATPase system that was not inhibited. Calmodulin, in the concentration interval 0·30–0·90 μmol l ‐1 , did not further activate the ATPase system. Calmidazolium, which is a highly lipophilic substance, was a competitive inhibitor of the Mg 2+ ‐ and Ca 2+ ‐dependent ATPase and half maximal inhibition was attained at 2–3 μmoll ‐1 calmidazolium. This inhibition was antagonized to a moderate degree (25%, P < 0·02) by calmodulin, 0·60 μmol ‐1 . Quercetin, at concentrations of 30–60 μmol l ‐1 , did not influence the prostasome membrane ATPase in any direction. Oleate was an inhibitor of the ATPase system at any concentration up to 50 μmol l ‐1 . This inhibition was not counteracted to an appreciable extent by calmodulin. These results displayed a pattern giving support to the view that the Mg 2+ ‐ and Ca 2+ ‐dependent ATPase of the prostasome membrane may be the molecular basis for vectorial transport of Ca 2+ into prostasomes.