Steroid hormones pathway

Gonadotropin-releasing hormone is encoded from a single gene on the short arm of chromosome 8p21-p11. The human gene contains 4 exons; exon 2 encodes pro-GnRH, exon 3 and part of exon 2 and 4 encode the GAP protein, and exon 4 encodes a long 3′ untranslated region. Molecular processing occurs primarily in the nucleus of the cell body (soma). After transcription, the mRNA is transported to the cytoplasm where translation takes place and it is converted into the decapeptide. GnRH and its cleavage products, GAP and pro-GnRH, are then transported to the nerve terminals where they are secreted in tandem into the portal circulation. 187, 189, 190

Microbial catabolism of phytosterol side chains yields C-19 steroids, C-22 steroids, and 17-ketosteroids (. precursors to adrenocortical hormones and contraceptives ). [46] [47] [48] [49] The addition and modification of functional groups is key when producing the wide variety of medications available within this chemical classification. These modifications are performed using conventional organic synthesis and/or biotransformation techniques. [50] [51]

Genetic analysis of dauer-constitutive (Daf-c) and dauer-defective (Daf-d) mutants has defined four distinct pathways that regulate dauer arrest ( Gerisch et al., 2001 ; Gottlieb and Ruvkun, 1994 ; Jia et al., 2002 ; Riddle et al., 1981 ; Thomas et al., 1993 ; Vowels and Thomas, 1992 ). In the past decade, components of these and other pathways have been cloned and characterized, revealing the complex interplay of at least four evolutionarily conserved signal transduction pathways in regulating dauer formation.

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 compound cycloartenol, which contains a three-membered ring (C9, C10, C19) in lieu of the nuclear double bond of lanosterol. The side chains of the phytosterols, such as stigmasterol, and of the sterol ergosterol of yeasts and other fungi contain extra carbon atoms that are incorporated in reactions involving S -adenosylmethionine, which donates methyl groups in numerous biological processes. Although most plant tissues contain only traces of cholesterol, this sterol is the biogenetic precursor of such important plant steroids as the sapogenins , glycosides , and alkaloids . Because pregnane derivatives are intermediates in some of these transformations, plants and animals appear to have important features of steroid metabolism in common.

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Steroid hormones pathway

steroid hormones pathway

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 compound cycloartenol, which contains a three-membered ring (C9, C10, C19) in lieu of the nuclear double bond of lanosterol. The side chains of the phytosterols, such as stigmasterol, and of the sterol ergosterol of yeasts and other fungi contain extra carbon atoms that are incorporated in reactions involving S -adenosylmethionine, which donates methyl groups in numerous biological processes. Although most plant tissues contain only traces of cholesterol, this sterol is the biogenetic precursor of such important plant steroids as the sapogenins , glycosides , and alkaloids . Because pregnane derivatives are intermediates in some of these transformations, plants and animals appear to have important features of steroid metabolism in common.

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