Transcortin

Template:Short description Template:Infobox gene Transcortin, also known as corticosteroid-binding globulin (CBG) or serpin A6, is a protein produced in the liver in animals. In humans it is encoded by the SERPINA6 gene. It is an alpha-globulin.<ref name="pmid3299377">Template:Cite journal</ref><ref name="pmid7912884">Template:Cite journal</ref><ref name="entrez">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

FunctionEdit

This gene encodes an alpha-globulin protein with corticosteroid-binding properties. This is the major transport protein for glucocorticoids and progestins in the blood of most vertebrates. The gene localizes to a chromosomal region containing several closely related serine protease inhibitors (serpins).<ref name="entrez"/>

BindingEdit

Transcortin binds several steroid hormones at high rates:

Cortisol - Approximately 90% of the cortisol in circulation is bound to transcortin. (The rest is bound to serum albumin.) Cortisol is thought to be biologically active only when it is not bound to transcortin.Template:Citation needed
Cortisone<ref name="BittarBittar1997">Template:Cite book</ref>
Deoxycorticosterone (DOC)<ref name="BittarBittar1997" />
Corticosterone - About 78% of serum corticosterone is bound to transcortin.
Aldosterone - Approximately 17% of serum aldosterone is bound to transcortin, while another 47% is bound to serum albumin. The remaining 36% is free.<ref name="Principles and Practice of Endocrinology and Metabolism">Template:Cite book</ref>
Progesterone - Approximately 18% of serum progesterone is bound to transcortin, while another 80% of it is bound to serum albumin. The remaining 2% is free.<ref name="Negi2009">Template:Cite book</ref>
17α-Hydroxyprogesterone<ref name="BittarBittar1997" />

In addition, approximately 4% of serum testosterone is bound to transcortin.<ref name="pmid7195404">Template:Cite journal</ref> A similarly small fraction of serum estradiol is bound to transcortin as well.Template:Citation needed

SynthesisEdit

Transcortin is produced by the liver and is increased by estrogens.<ref name="pmid4284083">Template:Cite journal</ref>

Clinical significanceEdit

Mutations in this gene are rare. Only four mutations have been described, often in association with fatigue and chronic pain.<ref name="pmid22013108">Template:Cite journal</ref> The mechanism for these symptoms is not known. This condition must be distinguished from secondary hypocortisolism. Exogenous hydrocortisone does not appear to improve the fatigue.Template:Cn

Hepatic synthesis of corticosteroid-binding globulin more than doubles in pregnancy; that is, bound plasma cortisol in term pregnancy is approximately 2 to 3 times that of nonpregnant women.<ref name="isbn0-683-30665-0">Template:Cite book</ref><ref name="Gronowski2004">Template:Cite book</ref>

ReferencesEdit

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External linksEdit

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The MEROPS online database for peptidases and their inhibitors: I04.954
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Template:Carrier proteins Template:Alpha globulins Template:Serpins Template:Glycoproteins Template:Glucocorticoidics Template:Mineralocorticoidics Template:Progestogenics Template:Use dmy dates