Editing Steroid (section)

== Species distribution ==

Steroids are present across all domains of life, including [[bacteria]], [[archaea]], and [[eukaryote]]s. In eukaryotes, steroids are particularly abundant in fungi, plants, and animals.<ref name="Britannica-Biological-significance-of-steroids">{{cite encyclopedia|url=https://www.britannica.com/science/steroid/Biological-significance-of-steroids|title=Biological significance of steroids|access-date=12 February 2024|archive-date=12 February 2024|archive-url=https://web.archive.org/web/20240212190424/https://www.britannica.com/science/steroid/Biological-significance-of-steroids|url-status=live}}</ref><ref name="libre">{{cite news | url=https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_%28Boundless%29/17%3A_Industrial_Microbiology/17.02%3A_Microbial_Products_in_the_Health_Industry/17.2C%3A_Steroids | title=17.2C: Steroids | newspaper=Biology Libretexts | date=3 July 2018 | access-date=12 February 2024 | archive-date=12 February 2024 | archive-url=https://web.archive.org/web/20240212190425/https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Boundless)/17:_Industrial_Microbiology/17.02:_Microbial_Products_in_the_Health_Industry/17.2C:_Steroids | url-status=live }}</ref>

=== Eukaryotic ===

[[Eukaryote|Eukaryotic]] cells, encompassing animals, plants, fungi, and protists, are characterized by their complex cellular structures, including a true nucleus and membrane-bound organelles.<ref>{{Cite journal |title=Steroids distribution |date=2021 |doi=10.1073/pnas.2101276118 |pmid=34131078 |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=118 |issue=25 |pmc=8237579 | vauthors = Hoshino Y, Gaucher EA |doi-access=free }}</ref> Sterols, a subgroup of steroids, play crucial roles in maintaining membrane fluidity, supporting cell signaling, and enhancing stress tolerance. These compounds are integral to eukaryotic membranes, where they contribute to membrane integrity and functionality.<ref>{{Cite web |title=Steroids distribution |url=https://www.drugs.com/monograph/calcium-salts.html |access-date=17 May 2024 |archive-date=18 January 2017 |archive-url=https://web.archive.org/web/20170118041341/https://www.drugs.com/monograph/calcium-salts.html |url-status=bot: unknown }}</ref>

During [[eukaryogenesis]]—the evolutionary process that gave rise to modern eukaryotic cells—steroids likely facilitated the endosymbiotic acquisition of mitochondria.<ref>{{Cite journal |title=Species distribution |date=2021 |doi=10.1073/pnas.2101276118 |pmid=34131078 |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=118 |issue=25 |pmc=8237579 | vauthors = Hoshino Y, Gaucher EA |doi-access=free }}</ref>

=== Prokaryotic ===

Although sterol biosynthesis is rare in prokaryotes, certain bacteria, including ''[[Methylococcus capsulatus]]'', specific [[methanotroph]]s, [[myxobacteria]], and the [[planctomycete]] ''[[Gemmata obscuriglobus]]'', are capable of producing sterols. In ''G. obscuriglobus'', sterols are essential for cell viability, but their roles in other bacteria remain poorly understood.<ref name="Franke_2021">{{cite book | vauthors = Franke JD | chapter = Sterol Biosynthetic Pathways and Their Function in Bacteria. | veditors = Villa TG, de Miguel Bouzas T | title = Developmental Biology in Prokaryotes and Lower Eukaryotes | date = 2021 | pages = 215-227 | doi = 10.1007/978-3-030-77595-7_9 | isbn = 978-3-030-77595-7 | location = Cham | publisher = Springer}}</ref> 

Prokaryotic sterol synthesis involves the tetracyclic steroid framework, as found in [[myxobacteria]],<ref name="pmid12519197">{{cite journal | vauthors = Bode HB, Zeggel B, Silakowski B, Wenzel SC, Reichenbach H, Müller R | title = Steroid biosynthesis in prokaryotes: identification of myxobacterial steroids and cloning of the first bacterial 2,3(S)-oxidosqualene cyclase from the myxobacterium Stigmatella aurantiaca | journal = Molecular Microbiology | volume = 47 | issue = 2 | pages = 471–81 | date = Jan 2003 | pmid = 12519197 | doi = 10.1046/j.1365-2958.2003.03309.x | s2cid = 37959511 | doi-access = }}</ref> as well as [[hopanoids]], pentacyclic lipids that regulate bacterial membrane functions.<ref name="pmid21531832">{{cite journal | vauthors = Siedenburg G, Jendrossek D | title = Squalene-hopene cyclases | journal = Applied and Environmental Microbiology | volume = 77 | issue = 12 | pages = 3905–15 | date = Jun 2011 | pmid = 21531832 | pmc = 3131620 | doi = 10.1128/AEM.00300-11 | bibcode = 2011ApEnM..77.3905S }}</ref> These sterol biosynthetic pathways may have originated in bacteria or been transferred from [[eukaryote]]s.<ref name="pmid20333205">{{cite journal | vauthors = Desmond E, Gribaldo S | title = Phylogenomics of sterol synthesis: insights into the origin, evolution, and diversity of a key eukaryotic feature | journal = Genome Biology and Evolution | volume = 1 | pages = 364–81 | year = 2009 | pmid = 20333205 | pmc = 2817430 | doi = 10.1093/gbe/evp036 }}</ref> 

Sterol synthesis depends on two key enzymes: [[squalene monooxygenase]] and [[oxidosqualene cyclase]]. Phylogenetic analyses of oxidosqualene cyclase (Osc) suggest that some bacterial Osc genes may have been acquired via [[horizontal gene transfer]] from eukaryotes, as certain bacterial Osc proteins closely resemble their eukaryotic homologs.<ref name="Franke_2021" />

=== Fungal ===
Fungal steroids include the [[ergosterol]]s, which are involved in maintaining the integrity of the fungal cellular membrane. Various [[antifungal drugs]], such as [[amphotericin B]] and [[azole antifungals]], utilize this information to kill [[pathogenic]] fungi.<ref name="Bhetariya-2017">{{cite book | vauthors = Bhetariya PJ, Sharma N, Singh P, Tripathi P, Upadhyay SK, Gautam P | veditors = Arora C, Sajid A, Kalia V  | title=Drug Resistance in Bacteria, Fungi, Malaria, and Cancer|publisher=Springer|isbn=978-3-319-48683-3|language=en|chapter=Human Fungal Pathogens and Drug Resistance Against Azole Drugs| date = 21 March 2017}}</ref> Fungi can alter their ergosterol content (e.g. through loss of function mutations in the enzymes [[C-5 sterol desaturase|ERG3]] or [[Sterol 24-C-methyltransferase|ERG6]], inducing depletion of ergosterol, or mutations that decrease the ergosterol content) to develop resistance to drugs that target ergosterol.<ref name="Kavanagh Fungi" />

Ergosterol is analogous to the [[cholesterol]] found in the cellular membranes of animals (including humans), or the [[phytosterols]] found in the cellular membranes of plants.<ref name="Kavanagh Fungi">{{cite book| veditors = Kavanagh K |title=Fungi: Biology and Applications|date=8 September 2017|publisher=John Wiley & Sons, Inc.|isbn=978-1-119-37431-2|language=en}}</ref> All mushrooms contain large quantities of ergosterol, in the range of tens to hundreds of milligrams per 100 grams of dry weight.<ref name="Kavanagh Fungi" /> Oxygen is necessary for the synthesis of [[ergosterol]] in fungi.<ref name="Kavanagh Fungi" />

Ergosterol is responsible for the [[vitamin D]] content found in mushrooms; ergosterol is chemically converted into provitamin D2 by exposure to [[ultraviolet light]].<ref name="Kavanagh Fungi" /> Provitamin D2 spontaneously forms vitamin D2.<ref name="Kavanagh Fungi" /> However, not all fungi utilize ergosterol in their cellular membranes; for example, the pathogenic fungal species ''[[Pneumocystis jirovecii]]'' does not, which has important clinical implications (given the mechanism of action of many antifungal drugs). Using the fungus ''[[Saccharomyces cerevisiae]]'' as an example, other major steroids include [[ergosta‐5,7,22,24(28)‐tetraen‐3β‐ol]], [[zymosterol]], and [[lanosterol]]. ''S. cerevisiae'' utilizes [[5,6‐dihydroergosterol]] in place of ergosterol in its cell membrane.<ref name="Kavanagh Fungi" />

=== Plant ===
Plant steroids include steroidal [[alkaloid]]s found in [[Solanaceae]]<ref name="pmid12946402">{{cite journal | vauthors = Wink M | title = Evolution of secondary metabolites from an ecological and molecular phylogenetic perspective | journal = Phytochemistry | volume = 64 | issue = 1 | pages = 3–19 | date = Sep 2003 | pmid = 12946402 | doi = 10.1016/S0031-9422(03)00300-5 | bibcode = 2003PChem..64....3W }}</ref> and [[Melanthiaceae]] (specially the genus [[Veratrum]]),<ref name="Maappotw1">{{cite book | vauthors = Wink M, Van Wyk BE |title=Mind-altering and poisonous plants of the world |date=2008 |publisher=Timber press inc. |location=Portland (Oregon USA) and Salusbury (London England) |isbn=978-0-88192-952-2 |pages=252, 253 and 254}}</ref> [[cardiac glycoside]]s,<ref name="Maappotw2">{{cite book | vauthors = Wink M, van Wyk BE |title=Mind-altering and poisonous plants of the world |date=2008 |publisher=Timber press inc. |location=Portland (Oregon USA) and Salusbury (London England) |isbn=978-0-88192-952-2 |pages=324, 325 and 326}}</ref> the [[phytosterol]]s and the [[brassinosteroid]]s (which include several plant hormones).

=== Animal ===
Animal steroids include compounds of [[vertebrate]] and [[insect]] origin, the latter including [[ecdysteroid]]s such as [[ecdysterone]] (controlling molting in some species). Vertebrate examples include the [[steroid hormones]] and cholesterol; the latter is a structural component of [[cell membranes]] that helps determine the fluidity of [[cell membranes]] and is a principal constituent of [[Atheroma|plaque]] (implicated in [[atherosclerosis]]). Steroid hormones include:
* [[Sex hormone]]s, which influence [[sexual differentiation|sex differences]] and support [[puberty]] and [[reproduction]]. These include [[androgen]]s, [[estrogen]]s, and [[progestogen]]s.
* [[Corticosteroid]]s, including most synthetic steroid drugs, with [[natural product]] classes the [[glucocorticoid]]s (which regulate many aspects of [[metabolism]] and [[immune system|immune function]]) and the [[mineralocorticoid]]s (which help maintain blood volume and control [[kidney|renal]] excretion of [[electrolyte]]s)
* [[Anabolic steroid]]s, [[natural product|natural]] and synthetic, which interact with androgen receptors to increase muscle and bone synthesis. In popular use, the term "steroids" often refers to anabolic steroids.