Site of steroid hormone synthesis

Steroidogenesis Steroid hormones are derivatives of cholesterol that are synthesized by a variety of tissues, most prominently the The basic Biosynthesis of steroid hormones requires a battery of oxidative enzymes located in both mitochondria and endoplasmic reticulum. The rate-limiting step in this process is the transport of free cholesterol from the cytoplasm into mitochondria. Within mitochondria, cholesterol is converted to pregnenolone by an enzyme in the inner membrane called CYP11A1. Pregnenolone itself is not a hormone, but is the immediate precursor for the synthesis of all of the steroid hormones. The following table delineates the enzymes required to synthesize the major classes of steroid hormones. Common name "Old" name Current name Side-chain cleavage enzyme; desmolase P450 SCC CYP11A1 3 beta-hydroxysteroid dehydrogenase 3 beta-HSD 3 beta-HSD 17 alpha-hydroxylase/17,20 lyase P450 C17 CYP17 21-hydroxylase P450 C21 CYP21A2 11 beta-hydroxylase P450 C11 CYP11B1 Aldosterone synthase P450 C11AS CYP11B2 Aromatase P450 aro CYP19 Typically, endocrinologists classify steroid hormones into five groups of molecules, based primarily on the receptor to which they bind: • Glucocorticoids; cortisol is the major representative in most mammals • Mineralocorticoids; aldosterone being most prominent • Androgens such as testosterone • Estrogens, including estrodiol and estrone • Progestogens (also known a progestins) such as progesterone The biosynthetic pathways for major repre...

Steroids are probably Cholesterol and other steroids are biosynthesized by extension of the enzyme pathway by which terpenoids are synthesized. Acetate fragments derived from common nutrient materials are converted into mevalonic acid, from which the The principal forms in which cholesterol is excreted by vertebrates are the In vertebrates, cholesterol is the central Many tissues, but mainly the liver, metabolize the steroid hormones to physiologically inactive products that are voided mainly in the Steroid metabolism in The early steps in the biosynthesis of steroids of both plants and animals are the same, except that in plants lanosterol is replaced by the related S-adenosylmethionine, which donates

Peptide hormones are composed of polypeptide chains with a size ranging from three to hundreds of amino acids. Peptide hormone synthesis involves several steps occurring in the nucleus and cytoplasm of secretory cells, including gene transcription into the precursor nuclear ribonucleic acid, posttranscriptional modifications of the precursor messenger ribonucleic acid transcript, translation of the mature messenger ribonucleic acid, and cotranslational and posttranslational modifications of the hormonal peptide. Synthesis of peptide hormones is regulated at one or more of the above-mentioned biosynthetic steps in order to meet the secretory requirements of endocrine glands. Once they are synthesized, peptide hormones are packaged into secretory granules until appropriate stimuli result in their secretion into the extracellular space. Secretion is not uniform, but rather follows pulsatile patterns and rhythmic changes which, in association with feedback mechanisms, ensure that hormone production is adequate and prevent the excessive release of hormones. Most peptide hormones are water soluble and therefore do not require carrier proteins to circulate in the blood stream. This property results in rapid hormone degradation by plasma proteases and a shorter half-life and duration of action compared to other types of hormones, such as steroid and thyroid hormones. Keywords • Peptide hormone • Synthesis • Secretion • Transport • Gene transcription • Posttranscriptional processin...

Mitochondria are essential sites for , and and ferredoxin. This enzyme system converts cholesterol to , including 3β-hydroxysteroid dehydrogenase, 11β-hydroxylase and The access of cholesterol to the mitochondria is regulated by the kDa protein (TSPO), the voltage-dependent anion chanel (VDAC-1), TSPO-associated protein 7 (PAP7, ACBD3), and have been described for StAR and for all the mitochondrial steroidogenic enzymes, but not for the Introduction Six classes of steroid hormones, all of which are indispensable for mammalian life, are made from cholesterol via complex biosynthetic pathways that are initiated by specialized, tissue-specific enzymes found in mitochondria. These hormones include glucocorticoids (cortisol, corticosterone) and mineralocorticoids (aldosterone) produced in the adrenal cortex; estrogens (estradiol), progestins (progesterone) and androgens (testosterone, dihydrotestosterone) produced in the gonads; and calciferols (1,25-dihydroxy vitamin D [1,25OH 2D]) produced in the kidney. The biosynthesis of the steroid hormones (Miller and Auchus, 2011) and of 1,25OH 2D (a sterol) (Feldman et al., 2013) from cholesterol have been reviewed recently. There are two specialized aspects to the mitochondria of these steroidogenic tissues – the specialized mechanisms by which cholesterol is delivered to the mitochondria and the specialized intra-mitochondrial enzymes that paricipate in the synthesis of hormonal steroids. Section snippets Sources of cholesterol The i...

Peptide hormones are composed of polypeptide chains with a size ranging from three to hundreds of amino acids. Peptide hormone synthesis involves several steps occurring in the nucleus and cytoplasm of secretory cells, including gene transcription into the precursor nuclear ribonucleic acid, posttranscriptional modifications of the precursor messenger ribonucleic acid transcript, translation of the mature messenger ribonucleic acid, and cotranslational and posttranslational modifications of the hormonal peptide. Synthesis of peptide hormones is regulated at one or more of the above-mentioned biosynthetic steps in order to meet the secretory requirements of endocrine glands. Once they are synthesized, peptide hormones are packaged into secretory granules until appropriate stimuli result in their secretion into the extracellular space. Secretion is not uniform, but rather follows pulsatile patterns and rhythmic changes which, in association with feedback mechanisms, ensure that hormone production is adequate and prevent the excessive release of hormones. Most peptide hormones are water soluble and therefore do not require carrier proteins to circulate in the blood stream. This property results in rapid hormone degradation by plasma proteases and a shorter half-life and duration of action compared to other types of hormones, such as steroid and thyroid hormones. Keywords • Peptide hormone • Synthesis • Secretion • Transport • Gene transcription • Posttranscriptional processin...

Steroids are probably Cholesterol and other steroids are biosynthesized by extension of the enzyme pathway by which terpenoids are synthesized. Acetate fragments derived from common nutrient materials are converted into mevalonic acid, from which the The principal forms in which cholesterol is excreted by vertebrates are the In vertebrates, cholesterol is the central Many tissues, but mainly the liver, metabolize the steroid hormones to physiologically inactive products that are voided mainly in the Steroid metabolism in The early steps in the biosynthesis of steroids of both plants and animals are the same, except that in plants lanosterol is replaced by the related S-adenosylmethionine, which donates

Mitochondria are essential sites for , and and ferredoxin. This enzyme system converts cholesterol to , including 3β-hydroxysteroid dehydrogenase, 11β-hydroxylase and The access of cholesterol to the mitochondria is regulated by the kDa protein (TSPO), the voltage-dependent anion chanel (VDAC-1), TSPO-associated protein 7 (PAP7, ACBD3), and have been described for StAR and for all the mitochondrial steroidogenic enzymes, but not for the Introduction Six classes of steroid hormones, all of which are indispensable for mammalian life, are made from cholesterol via complex biosynthetic pathways that are initiated by specialized, tissue-specific enzymes found in mitochondria. These hormones include glucocorticoids (cortisol, corticosterone) and mineralocorticoids (aldosterone) produced in the adrenal cortex; estrogens (estradiol), progestins (progesterone) and androgens (testosterone, dihydrotestosterone) produced in the gonads; and calciferols (1,25-dihydroxy vitamin D [1,25OH 2D]) produced in the kidney. The biosynthesis of the steroid hormones (Miller and Auchus, 2011) and of 1,25OH 2D (a sterol) (Feldman et al., 2013) from cholesterol have been reviewed recently. There are two specialized aspects to the mitochondria of these steroidogenic tissues – the specialized mechanisms by which cholesterol is delivered to the mitochondria and the specialized intra-mitochondrial enzymes that paricipate in the synthesis of hormonal steroids. Section snippets Sources of cholesterol The i...

Steroidogenesis Steroid hormones are derivatives of cholesterol that are synthesized by a variety of tissues, most prominently the The basic Biosynthesis of steroid hormones requires a battery of oxidative enzymes located in both mitochondria and endoplasmic reticulum. The rate-limiting step in this process is the transport of free cholesterol from the cytoplasm into mitochondria. Within mitochondria, cholesterol is converted to pregnenolone by an enzyme in the inner membrane called CYP11A1. Pregnenolone itself is not a hormone, but is the immediate precursor for the synthesis of all of the steroid hormones. The following table delineates the enzymes required to synthesize the major classes of steroid hormones. Common name "Old" name Current name Side-chain cleavage enzyme; desmolase P450 SCC CYP11A1 3 beta-hydroxysteroid dehydrogenase 3 beta-HSD 3 beta-HSD 17 alpha-hydroxylase/17,20 lyase P450 C17 CYP17 21-hydroxylase P450 C21 CYP21A2 11 beta-hydroxylase P450 C11 CYP11B1 Aldosterone synthase P450 C11AS CYP11B2 Aromatase P450 aro CYP19 Typically, endocrinologists classify steroid hormones into five groups of molecules, based primarily on the receptor to which they bind: • Glucocorticoids; cortisol is the major representative in most mammals • Mineralocorticoids; aldosterone being most prominent • Androgens such as testosterone • Estrogens, including estrodiol and estrone • Progestogens (also known a progestins) such as progesterone The biosynthetic pathways for major repre...

Peptide hormones are composed of polypeptide chains with a size ranging from three to hundreds of amino acids. Peptide hormone synthesis involves several steps occurring in the nucleus and cytoplasm of secretory cells, including gene transcription into the precursor nuclear ribonucleic acid, posttranscriptional modifications of the precursor messenger ribonucleic acid transcript, translation of the mature messenger ribonucleic acid, and cotranslational and posttranslational modifications of the hormonal peptide. Synthesis of peptide hormones is regulated at one or more of the above-mentioned biosynthetic steps in order to meet the secretory requirements of endocrine glands. Once they are synthesized, peptide hormones are packaged into secretory granules until appropriate stimuli result in their secretion into the extracellular space. Secretion is not uniform, but rather follows pulsatile patterns and rhythmic changes which, in association with feedback mechanisms, ensure that hormone production is adequate and prevent the excessive release of hormones. Most peptide hormones are water soluble and therefore do not require carrier proteins to circulate in the blood stream. This property results in rapid hormone degradation by plasma proteases and a shorter half-life and duration of action compared to other types of hormones, such as steroid and thyroid hormones. Keywords • Peptide hormone • Synthesis • Secretion • Transport • Gene transcription • Posttranscriptional processin...

Mitochondria are essential sites for , and and ferredoxin. This enzyme system converts cholesterol to , including 3β-hydroxysteroid dehydrogenase, 11β-hydroxylase and The access of cholesterol to the mitochondria is regulated by the kDa protein (TSPO), the voltage-dependent anion chanel (VDAC-1), TSPO-associated protein 7 (PAP7, ACBD3), and have been described for StAR and for all the mitochondrial steroidogenic enzymes, but not for the Introduction Six classes of steroid hormones, all of which are indispensable for mammalian life, are made from cholesterol via complex biosynthetic pathways that are initiated by specialized, tissue-specific enzymes found in mitochondria. These hormones include glucocorticoids (cortisol, corticosterone) and mineralocorticoids (aldosterone) produced in the adrenal cortex; estrogens (estradiol), progestins (progesterone) and androgens (testosterone, dihydrotestosterone) produced in the gonads; and calciferols (1,25-dihydroxy vitamin D [1,25OH 2D]) produced in the kidney. The biosynthesis of the steroid hormones (Miller and Auchus, 2011) and of 1,25OH 2D (a sterol) (Feldman et al., 2013) from cholesterol have been reviewed recently. There are two specialized aspects to the mitochondria of these steroidogenic tissues – the specialized mechanisms by which cholesterol is delivered to the mitochondria and the specialized intra-mitochondrial enzymes that paricipate in the synthesis of hormonal steroids. Section snippets Sources of cholesterol The i...