Mammalian aromatases

Abstract

Aromatase is the enzyme complex that catalyses the synthesis of oestrogens from androgens, and therefore it has unique potential to influence the physiological balance between the sex steroid hormones. Both aromatase cytochrome P450 (P450arom) and NADPH-cytochrome P450 reductase (reductase), the two essential components of the enzyme complex, are highly conserved among mammals and vertebrates. Aromatase expression occurs in the gonads and brain, and is essential for reproductive development and fertility. Of interest are the complex mechanisms involving alternative promoter utilization that have evolved to control tissue-specific expression in these tissues. In addition, in a number of species, including humans, expression of aromatase has a broader tissue distribution, including placenta, adipose and bone. The relevance of oestrogen synthesis and possibly androgen metabolism in these peripheral sites of expression is now becoming clear from studies in P450arom knockout (ArKO) mice and from genetic defects recognized recently in both men and women. Important species differences in the physiological roles of aromatase expression are also likely to emerge, despite the highly conserved nature of the enzyme system. The identification of functionally distinct, tissue-specific isozymes of P450arom in at least one mammal, pigs, and several species of fish indicates that there are additional subtle, but physiologically significant, species-specific roles for aromatase. Comparative studies of mammalian and other vertebrate aromatases will expand understanding of the role played by this ancient enzyme system in the evolution of reproduction and the adaptive influence of oestrogen synthesis on general health and well being.

Adrenal glands of Spix's yellow-toothed cavy (Galea spixii, Wagler, 1831): morphological and morphometric aspects

“…In other study, cytochrome enzymes P450c17 and P450 aromatase were found in vaginal tissue throughout estrous cycle suggesting a local production of androgen and estrogen hormones (Santos et al, 2014b) in agreement with several studies that have shown a wide variety of different production sites of steroid hormones in different mammalian species (Conley and Hinshelwood, 2001;Conley et al, 2004).…”

Expression of steroidogenic enzymes during equine testicular development

“…P450arom is present in the ER of numerous vertebrate tissues and has been the focus of studies in numerous species (Conley & Hinshelwood 2001). According to Carreau et al (1999) and Hess et al (2001), the primary source of estrogen is the Sertoli cell in the immature testis and Leydig and germ cells in the mature testis.…”

Oestrogen action and male fertility: experimental and clinical findings

“…1 The balance of androgen and oestrogen X. Li et al localization and the different 5 0 UTR CYP19A1 variants, each transcript generates a highly conserved 55 kDa aromatase protein [17]. Thus, the spatio-temporal expression of CYP19A1 is critical for the maintenance of the oestrogen/androgen balance during foetal and postnatal development.…”