Neha Patil (Editor)

Transcortin

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Species
  
Human

Entrez
  
866

Human
  
Mouse

Ensembl
  
n/a

Transcortin

Aliases
  
SERPINA6, CBG, serpin family A member 6

External IDs
  
OMIM: 122500 MGI: 88278 HomoloGene: 20417 GeneCards: SERPINA6

Transcortin, also known as corticosteroid-binding globulin (CBG) or serpin A6 is a protein that in humans is encoded by the SERPINA6 gene. It is an alpha-globulin.

Contents

Function

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) which have evolved by duplication events.

Binding

Transcortin binds several steroid hormones at high rates:

  • Cortisol - Approximately 75% 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.
  • Cortisone
  • Deoxycorticosterone (DOC)
  • 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.
  • 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.
  • 17α-Hydroxyprogesterone

    • In addition, approximately 4% of serum testosterone is bound to transcortin. A similarly small fraction of serum estradiol is bound to transcortin as well.

    Synthesis

    Transcortin is produced by the liver and is increased by estrogens.

    Clinical significance

    Mutations in this gene are rare. Only four mutations have been described, often in association with fatigue and chronic pain. This mechanism for these symptoms is not known. This condition must be distinguished from secondary hypocortisolism. Exogenous hydrocortisone does not appear to improve the fatigue.

    Hepatic synthesis of corticosteroid-binding globulin more than doubles in pregnancy; that is, unbound plasma cortisol in term pregnancy is approximately 2.5 times that of nonpregnant women.

    References

    Transcortin Wikipedia
    (Text) CC BY-SA