Vr. Gujrati et Bvr. Sastry, Metabolic fate of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine by human spermatozoa - Biosynthesis and biodegradation, LIFE SCI, 68(15), 2001, pp. 1787-1805
Human spermatozoa can synthesise 1-alkyl-2-acetyl-glycerophosphocholine (AA
GPC) in small amount by acetyltransferase (AT) in absence of any stimulus,
but can actively catabolise it by acetyl hydrolase (HY). Seminal plasma, on
the other hand, was devoid of anabolic enzyme albeit enrich in catabolic e
nzyme, suggesting as an active site for biodegradation of AAGPC secreted by
spermatozoa. Both, AT and HY exhibited pH-optima in range of 7.0-7.6 at wh
ich spermatozoa are maximum viable and motile. Ionophore A23187 and EGTA in
hibited AT, reversibly, whereas HY was inhibited by BSA, calcium-channel bl
ockers, and phospholipase A(2)-inhibitors. Effect of aging-time on ejaculat
es exhibited decreased AT activity with increased HY activity along with un
changed calcium content of spermatozoa. Serotonin in vitro studies showed a
pro-aggregator role on agglutination of spermatozoa. Viscid / long liquefa
ction time ejaculates exhibited raised AT activity and calcium contents wit
h decreased HY activity in spermatozoa and high degree of agglutination. St
udies with dithiothreitol-treatment indeed helped in liquefaction but level
s of both enzymes remained status quo, suggesting existence of both pathway
s: remodelling of membrane phospholipids and de novo synthesis of AAGPC in
spermatozoa, earlier being pre-dominant. We have proposed a role of AAGPC-S
erotonin-Calcium in agglutination and liquefaction of spermatozoa, a vital
aspect in normal fertility. (C) 2001 Elsevier Science Inc. All rights reser
ved.