Metabolic fate of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine by human spermatozoa - Biosynthesis and biodegradation

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.