Phospholipases modulate immature pig testicular androgen and 16-androstene biosynthetic pathways in vitro.
The role of membrane phospholipids in porcine testicular androgen and 16-androstene biosynthesis was examined by monitoring the effects of phospholipase treatments on the activities of the steroid transforming enzymes. Untreated (control) microsomes from immature pig testes converted pregnenolone to 17-hydroxypregnenolone and DHA to 5,16-androstadien-3 beta-ol (andien-beta) and 4,16-androstadien-3-one (dienone) in the 16-androstene pathway, these metabolites accounting for most (65%) of the pregnenolone converted. The 4-ene steroids in the androgen pathway (progesterone, 17-hydroxyprogesterone, androstenedione and testosterone) totalled less than 10% of the pregnenolone metabolites. No estrogens or 5 alpha-reduced metabolites were detected. Treatment with phospholipase A2 or C, decreased the conversion of pregnenolone to 4-ene-3-oxo steroids but did not decrease the quantities of 5-ene-3 beta-hydroxysteroids. Confirmation of these findings was obtained by measuring the individual enzymatic steps. Phospholipases A2 and C significantly reduced the conversion of DHA to androstenedione and andien-beta to dienone but did not affect 17-hydroxylase or 'andien-beta-synthetase'. However, when the C-17, 20 lyase step was measured alone, phospholipase C decreased the quantity of androstenedione produced indicating that the side-chain cleavage reaction may involve a lipid component. The different effects of phospholipases on these enzymes suggests that pregnenolone metabolism may be regulated by alterations in the membrane microenvironment.
Cooke
G M
GM
Department of d'Anatomie et Physiologie Animale, Faculté de Médecine Vétérinaire, Université de Montréal, Québec, Canada.
D000446:Aldehyde-Lyases / Q000378:metabolism; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D006913:Hydroxysteroid Dehydrogenases / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D009097:Multienzyme Complexes / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011284:Pregnenolone / Q000378:metabolism*; D011375:Progesterone Reductase / Q000378:metabolism; D012741:Sexual Maturation; D013254:Steroid 17-alpha-Hydroxylase; D013251:Steroid Isomerases / Q000378:metabolism; D013552:Swine; D013737:Testis / Q000201:enzymology*; D010738:Type C Phospholipases / Q000378:metabolism*
C021425:3 beta-hydroxysteroid oxidoreductase-delta(5) 3-ketosteroid isomerase; D009097:Multienzyme Complexes; D011284:Pregnenolone; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; C019701:androsta-5,16-dien-3 beta-ol synthetase; D006913:Hydroxysteroid Dehydrogenases; D011375:Progesterone Reductase; D013254:Steroid 17-alpha-Hydroxylase; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D000446:Aldehyde-Lyases; D013251:Steroid Isomerases