Ecto-diadenosine polyphosphates hydrolase activity on human prostasomes.
BACKGROUND
Ecto-diadenosine polyphosphates are ubiquitous compounds with several physiological roles. Ecto-diadenosine polyphosphates hydrolase control their actions by degrading and terminating their signaling. The present work deals with the identification and partial characterization of ecto-diadenosine polyphosphates hydrolase on human prostasomes.


METHODS
Reverse-phase and paired-ion HPLC techniques have been used.


RESULTS
Prostasomes have an ecto-diadenosine polyphosphates hydrolase that leads to the degradation of several diadenosine compounds. Kinetic parameters of the enzyme show that diadenosine tetraphosphate is the preferred substrate that is further metabolized by the prostasome-ecto-nucleotidases to adenosine. The ecto-enzyme is bound to the prostasome-membranes through a GPI-anchor and is activated by physiological concentration of Ca+2, Mg+2, and Mn+2. Its optimum pH is also in the slightly alkaline physiological range. Human spermatozoa do not possess this hydrolytic activity, but they can acquire it after fusion with prostasomes.


CONCLUSIONS
The existence of an enzyme capable of degrading diadenosine compounds and can be transferred to human spermatozoa suggests new physiological implications for the role of prostasomes in fertilization.
Minelli
Alba
A
Dipartimento di Scienze Biochimiche e Biotecnologie Molecolari, Sezione di Biochimica Cellulare, Università di Perugia, Via del Giochetto, Perugia, Italy. albami@tin.it
Allegrucci
Cinzia
C
Liguori
Lavinia
L
Ronquist
Gunnar
G
D017766:Acid Anhydride Hydrolases / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D022162:Cytoplasmic Vesicles / Q000201:enzymology*; D015226:Dinucleoside Phosphates / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000494:pharmacology; D013094:Spermatozoa / Q000201:enzymology* / Q000378:metabolism; D010738:Type C Phospholipases / Q000494:pharmacology
D015226:Dinucleoside Phosphates; C012276:diadenosine pyrophosphate; D008345:Manganese; D010738:Type C Phospholipases; D017766:Acid Anhydride Hydrolases; C075829:diadenosine polyphosphate hydrolase; D008274:Magnesium; D002118:Calcium