Enhancement of aromatase activity by D-aspartic acid in the ovary of the lizard Podarcis s. sicula.
The present study investigated the role of D-aspartic acid (D-Asp) in ovarian steroidogenesis and its effect on aromatase activity in the lizard, Podarcis s. sicula. It was determined that D-Asp concentrations vary significantly during phases of the reproductive cycle: they vary inversely with testosterone concentrations and directly with oestradiol concentrations in the ovary and plasma. Experimental treatment showed that administration of D-Asp induces a decrease in testosterone and an increase in oestradiol, and that treatment with other amino acids (L-Asp, D-Glu and D-Ala) instead of D-Asp has no effects. Experiments in vitro confirmed these results. Furthermore, these experiments showed an increase in aromatase activity, as the addition of D-Asp either to fresh ovarian tissue homogenate or to acetonic powder of ovarian follicles induced a significant increase in the conversion of testosterone to oestradiol. Aromatase activity is four times greater in the presence of D-Asp than in its absence. However, almost equivalent values of the two K(m) values (both approximately 25 nmol l(-1)) indicate that aromatase has the same catalytic properties in both cases.
Assisi
L
L
Department of Zoology, Faculty of Science, University of Naples, Via Mezzocannone 8, 80134 Naples, Italy.
Botte
V
V
D'Aniello
A
A
Di Fiore
M M
MM
D000818:Animals; D001141:Aromatase / Q000378:metabolism*; D001224:Aspartic Acid / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D004958:Estradiol / Q000032:analysis / Q000097:blood; D005260:Female; D007700:Kinetics; D008116:Lizards / Q000378:metabolism*; D010053:Ovary / Q000737:chemistry / Q000187:drug effects* / Q000201:enzymology*; D013739:Testosterone / Q000032:analysis / Q000097:blood
D001224:Aspartic Acid; D013739:Testosterone; D004958:Estradiol; D001141:Aromatase