Gen CYP11B1 kodira 11β -hidroksilazu – člana nadporodice enzimacitohromi P450. Proteini citohroma P450 su monooksigenaze, koje kataliziraju mnoge reakcije uključene u metabolizam lijekova i sintezu holesterola, steroida i drugih lipida. Proizvod ovog gena CYP11B1 je protein 11β-hidroksilaza. Ovaj protein nalazi se u unutrašnjoj membrani mitohondrija i uključen je u pretvorbu različitih steroida u kori nadbubrežne žlijezde. Za ovaj gen zabilježene su varijante transkripta koje kodiraju različite izoforme[6]
Ljudi imaju dva izoenzima sa 11β-hidroksilaznom aktivnošću: CYP11B1 i CYP11B2.
CYP11B1 (11β-hidroksilaza) eksprimiran je na visokim nivoima i reguliran je preko ACTH, dok je CYP11B2 (aldosteron-sintaza) obično ispoljena na niskim razinama i reguliran je angiotenzinom II. Osim aktivnosti 11β-hidroksilaze, oba izozima imaju i aktivnost 18-hidroksilaza.[11] Izozim CYP11B1 ima snažnu aktivnost 11β-hidroksilaze, ali je aktivnost 18-hidroksilaze samo jedna desetina CYP11B2.[12] Slaba aktivnost CYP11B1 18-hidroksilaze objašnjava zašto nadbubrežna žlijezda s potisnutom ekspresijom CYP11B2 nastavlja sintetizirati 18-hidroksikortikosteron.[13]
Slijedi neki steroidi, grupirani prema katalitskoj aktivnosti izoenzima CYP11B1:
Kao mitohondrijski P450 sistem, P450c11 ovisi o dva proteina za prijenos elektrona, adrenodoksin reduktazi i adrenodoksinu koji prenose dva elektrona iz NADPH u P450 za svaku reakciju monooksigenaze koju katalizira enzim. U većini aspekata ovaj proces prijenosa elektrona izgleda sličan onom u P450scc-sistemu koji katalizira cijepanje bočnog lanca holesterola.[26] Slično kao kod P450scc, proces prijenosa elektrona propušta, što dovodi do stvaranja superoksida. Brzina curenja elektrona tokom metabolizma ovisi o funkcionalnim skupinama supstrata steroida.[27]
Regulacija
Ekspresiju enzima u adrenokorteksnim ćelijama regulira trofni hormon kortikotropin (ACTH).[28]
^"Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^"Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^Lifton RP, Dluhy RG, Powers M, Rich GM, Gutkin M, Fallo F, et al. (septembar 1992). "Hereditary hypertension caused by chimaeric gene duplications and ectopic expression of aldosterone synthase". Nature Genetics. 2 (1): 66–74. doi:10.1038/ng0992-66. PMID1303253. S2CID975796.
^ ab"Entrez Gene: CYP11B1 cytochrome P450, family 11, subfamily B, polypeptide 1". National Center for Biotechnology Information. Pristupljeno 30. 11. 2020. This gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. This protein localizes to the mitochondrial inner membrane and is involved in the conversion of progesterone to cortisol in the adrenal cortex. Mutations in this gene cause congenital adrenal hyperplasia due to 11-beta-hydroxylase deficiency. Transcript variants encoding different isoforms have been noted for this gene.
^ abcdevan Rooyen D, Gent R, Barnard L, Swart AC (april 2018). "The in vitro metabolism of 11β-hydroxyprogesterone and 11-ketoprogesterone to 11-ketodihydrotestosterone in the backdoor pathway". The Journal of Steroid Biochemistry and Molecular Biology. 178: 203–212. doi:10.1016/j.jsbmb.2017.12.014. PMID29277707. S2CID3700135.
^Storbeck KH, Mostaghel EA (2019). "Canonical and Noncanonical Androgen Metabolism and Activity". Advances in Experimental Medicine and Biology. 1210: 239–277. doi:10.1007/978-3-030-32656-2_11. PMID31900912. CYP11B1 and 2 have also been shown to 11β-hydroxylate T, yielding 11β-hydroxytestosterone (11OHT), though the levels produced by the adrenal are low due to the limited availability of adrenal derived T
^Nicod J, Dick B, Frey FJ, Ferrari P (februar 2004). "Mutation analysis of CYP11B1 and CYP11B2 in patients with increased 18-hydroxycortisol production". Molecular and Cellular Endocrinology. 214 (1–2): 167–74. doi:10.1016/j.mce.2003.10.056. PMID15062555.
Helmberg A, Ausserer B, Kofler R (novembar 1992). "Frame shift by insertion of 2 basepairs in codon 394 of CYP11B1 causes congenital adrenal hyperplasia due to steroid 11 beta-hydroxylase deficiency". J. Clin. Endocrinol. Metab. 75 (5): 1278–81. doi:10.1210/jc.75.5.1278. PMID1430088.
Mornet E, Dupont J, Vitek A, White PC (decembar 1989). "Characterization of two genes encoding human steroid 11 beta-hydroxylase (P-450(11) beta)". J. Biol. Chem. 264 (35): 20961–7. PMID2592361.
Cargill M, Altshuler D, Ireland J, Sklar P, Ardlie K, Patil N, Shaw N, Lane CR, Lim EP, Kalyanaraman N, Nemesh J, Ziaugra L, Friedland L, Rolfe A, Warrington J, Lipshutz R, Daley GQ, Lander ES (juli 1999). "Characterization of single-nucleotide polymorphisms in coding regions of human genes". Nat. Genet. 22 (3): 231–8. doi:10.1038/10290. PMID10391209. S2CID195213008.
Halushka MK, Fan JB, Bentley K, Hsie L, Shen N, Weder A, Cooper R, Lipshutz R, Chakravarti A (juli 1999). "Patterns of single-nucleotide polymorphisms in candidate genes for blood-pressure homeostasis". Nat. Genet. 22 (3): 239–47. doi:10.1038/10297. PMID10391210. S2CID4636523.
Fisher A, Friel EC, Bernhardt R, Gomez-Sanchez C, Connell JM, Fraser R, Davies E (septembar 2001). "Effects of 18-hydroxylated steroids on corticosteroid production by human aldosterone synthase and 11beta-hydroxylase". J. Clin. Endocrinol. Metab. 86 (9): 4326–9. doi:10.1210/jc.86.9.4326. PMID11549669.
Hampf M, Dao NT, Hoan NT, Bernhardt R (septembar 2001). "Unequal crossing-over between aldosterone synthase and 11beta-hydroxylase genes causes congenital adrenal hyperplasia". J. Clin. Endocrinol. Metab. 86 (9): 4445–52. doi:10.1210/jc.86.9.4445. PMID11549691.