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Testosterone signaling in spermatogenesis, male fertility and infertility
Published in Rajender Singh, Molecular Signaling in Spermatogenesis and Male Infertility, 2019
Arijit Chakraborty, Vertika Singh, Kiran Singh, Rajender Singh
Steroidogenic enzymes responsible for the biosynthesis of various steroid hormones, including progestins, androgens, and estrogens from cholesterol, are several specific cytochrome P450 enzymes (CYPs), hydroxysteroid dehydrogenases (HSDs) and steroid reductases (6). The steroid hormones of the reproductive system are produced primarily in the gonads, although some steroidogenic chemical reactions are also found at peripheral tissue sites. For the male, the steroidogenic pathway is found in the testes and to some extent, in the adrenal glands. Within the testis, steroidogenesis occurs in the Leydig cell. The Leydig cells are interstitial cells that are interspersed between the seminiferous tubules. Inside the Leydig cells, the steroidogenic pathway begins in the cytoplasm and includes chemical reactions that occur in the mitochondria and smooth endoplasmic reticulum, where the final end-product, i.e., testosterone, is produced (7). Other active androgenic hormones are produced in the testis as well as at the peripheral tissue sites. In the pathway of steroid hormone biosynthesis, there are two major types of enzymes involved, cytochromes P450 and other steroid oxidoreductases.
Microsurgery in the Portal Area of the Rat
Published in Waldemar L. Olszewski, CRC Handbook of Microsurgery, 2019
Microsomal enzymes:glucose-6-phosphatase 3.1.3.9.acetanilide-hydroxylase (AAH)cytochrome-c-reductase (CCR)4en-steroid-reductase
Synthesis, Enzyme Localization, and Regulation of Neurosteroids
Published in Sheryl S. Smith, Neurosteroid Effects in the Central Nervous System, 2003
Pregnenolone produced from cholesterol can undergo one of two conversions: it may be 17α -hydroxylated to 17α -hydroxypregnenolone by P450c17 (see below), or converted to progesterone by the enzyme 3β HSD (Figure 1.1). 3β HSD has two distinct enzymatic activities: 3β -dehydrogenation and isomerization of the double bond from C5,6 in the B ring (Δ 5 steroids) to C4,5 in the A ring (Δ 4 steroids).27-29 This enzyme is encoded by multiple distinct genes, located on human chromosome 1, that are expressed in a tissue-specific manner. There are at least two forms of human 3β HSD and at least four forms of rodent 3β HSD. The human 3β HSD type I gene is expressed in the placenta, skin, mammary gland, and other tissues, including the brain, while a distinct human type II 3β HSD gene is expressed in adrenals and gonads. In rats, it is unknown whether the type I 3β HSD isoform alone or additional isoforms are expressed in the brain. The enzymes can be classified into two groups: those that function as dehydrogenase/isomerases and those that function as 3-keto-steroid reductases. 1.2.3.5 P450c17:
Finasteride and androgenic alopecia; from therapeutic options to medical implications
Published in Journal of Dermatological Treatment, 2020
Ion G. Motofei, David L. Rowland, Mircea Tampa, Maria-Isabela Sarbu, Madalina-Irina Mitran, Cristina-Iulia Mitran, Anca Pantea Stoian, Camelia C. Diaconu, Stana Paunica, Simona R. Georgescu
The 5α-reductase isoenzymes intervene in the metabolism of several steroid reactions, participating in the transformation of testosterone, progesterone, deoxycorticosterone, corticosterone, aldosterone, and androstenedione into their corresponding 5α-reduced metabolites (39). Thus far, three isoenzymes of 5α-reductase enzyme have been described, encoded by specific genes (SRD5A1, SRD5A2, and SRD5A3) (40,41). Inhibition of these enzymes decreases the level of dihydrotestosterone, such that the effect on androgenic alopecia has been investigated for various 5α-reductase inhibitory compounds. The steroidal inhibitory compounds are represented by finasteride (MK-906) and dutasteride (GG745), while nonsteroidal inhibitors may be either organic or inorganic compounds (coumarins, and isoflavones, catechins, zinc ions, etc.) (9). In addition to these compounds, some proteins (synaptic 2 and synaptic 2-like glycoproteins) exert 5α-reducing abilities to varying degrees (6). The type 1 of 5α‐steroid reductase isoenzyme is expressed especially in the sebaceous glands/scalp skin, brain, and liver, whereas type 2 of 5α‐steroid reductase is found predominantly in the dermal papilla of scalp hair, beard, chest hairs, liver, and prostate and seminal vesicles (28,29). Type 3 of 5α-reductase isoenzyme is found in several tissues, including the skin, brain, mammary glands, testicles, liver, and heart, among others (42).
Synthesis and evaluation of AKR1C inhibitory properties of A-ring halogenated oestrone derivatives
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Maša Sinreih, Rebeka Jójárt, Zoltán Kele, Tomaž Büdefeld, Gábor Paragi, Erzsébet Mernyák, Tea Lanišnik Rižner
The enzymes of the aldo-keto reductase (AKR) superfamily catalyse NADPH-dependent reductions in carbonyl-group-containing substrates, to provide their alcohols1. There are four human members of the AKR1C subfamily; AKR1C1–AKR1C3 are widely expressed, and AKR1C4 is liver specific. The AKR1C enzymes act as 3-keto, 17-keto, and 20-keto steroid reductases, through which they regulate the actions of androgens, oestrogens, and progestagens at the pre-receptor level2. Differential expression of the genes that encode the AKR1C isoforms has been reported for a wide variety of cancers, including breast, prostate, and endometrial cancers, and also in benign pathologies, including endometriosis2–4.