Transcortin, also known ascorticosteroid-binding globulin (CBG) orserpin A6, is aprotein produced in the liver in animals. In humans it is encoded by the SERPINA6gene. It is analpha-globulin.[5][6][7]
This gene encodes analpha-globulin protein withcorticosteroid-binding properties. This is the major transport protein forglucocorticoids andprogestins in the blood of most vertebrates. The gene localizes to a chromosomal region containing several closely related serine protease inhibitors (serpins).[7]
Transcortin binds several steroid hormones at high rates:
Cortisol - Approximately 90% of the cortisol in circulation is bound to transcortin. (The rest is bound toserum albumin.) Cortisol is thought to be biologically active only when it is not bound to transcortin.[citation needed]
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.[9]
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.[10]
In addition, approximately 4% of serumtestosterone is bound to transcortin.[11] A similarly small fraction of serumestradiol is bound to transcortin as well.[citation needed]
Mutations in this gene are rare. Only four mutations have been described, often in association with fatigue and chronic pain.[13] 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.[citation needed]
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.[14][15]
^Musa BU, Seal US, Doe RP (September 1965). "Elevation of certain plasma proteins in man following estrogen administration: a dose-response relationship".J. Clin. Endocrinol. Metab.25 (9):1163–6.doi:10.1210/jcem-25-9-1163.PMID4284083.
Rosner W, Beers PC, Awan T, Khan MS (1976). "Identification of corticosteroid-binding globulin in human milk: measurement with a filter disk assay".J. Clin. Endocrinol. Metab.42 (6):1064–73.doi:10.1210/jcem-42-6-1064.PMID932172.
Smith CL, Power SG, Hammond GL (1992). "A Leu----His substitution at residue 93 in human corticosteroid binding globulin results in reduced affinity for cortisol".J. Steroid Biochem. Mol. Biol.42 (7):671–6.doi:10.1016/0960-0760(92)90107-T.PMID1504007.S2CID45601231.
Loric S, Egloff M, Domingo M, et al. (1990). "Immunochemical characterization of corticosteroid-binding globulin in human bronchoalveolar fluid".Clin. Chim. Acta.186 (1):19–23.doi:10.1016/0009-8981(89)90198-8.PMID2612005.
Heubner A, Belovsky O, Müller W, et al. (1987). "Application of liquid-liquid partition chromatography in the simultaneous purification of sex-hormone-binding globulin and corticosteroid-binding globulin".J. Chromatogr.397:419–34.doi:10.1016/S0021-9673(01)85027-5.PMID2821037.
Bardin CW, Gunsalus GL, Musto NA, et al. (1988). "Corticosteroid binding globulin, testosterone-estradiol binding globulin, and androgen binding protein belong to protein families distinct from steroid receptors".J. Steroid Biochem.30 (1–6):131–9.doi:10.1016/0022-4731(88)90085-4.PMID3386241.
Hammond GL, Langley MS (1986). "Identification and measurement of sex hormone binding globulin (SHBG) and corticosteroid binding globulin (CBG) in human saliva".Acta Endocrinol.112 (4):603–8.doi:10.1530/acta.0.1120603.PMID3751467.
Agrimonti F, Frairia R, Fornaro D, et al. (1983). "Circadian and circaseptan rhythmicities in corticosteroid-binding globulin (CBG) binding activity of human milk".Chronobiologia.9 (3):281–90.PMID7172869.
Maruyama K, Sugano S (1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides".Gene.138 (1–2):171–4.doi:10.1016/0378-1119(94)90802-8.PMID8125298.
Avvakumov GV, Hammond GL (1994). "Glycosylation of human corticosteroid-binding globulin. Differential processing and significance of carbohydrate chains at individual sites".Biochemistry.33 (19):5759–65.doi:10.1021/bi00185a012.PMID8180202.
Van Baelen H, Power SG, Hammond GL (1993). "Decreased cortisol-binding affinity of transcortin Leuven is associated with an amino acid substitution at residue-93".Steroids.58 (6):275–7.doi:10.1016/0039-128X(93)90072-U.PMID8212073.S2CID25160586.
Misao R, Nakanishi Y, Fujimoto J, et al. (1996). "Expression of corticosteroid-binding globulin mRNA in human uterine endometrial cancers".Steroids.60 (10):720–4.doi:10.1016/0039-128X(95)00106-Z.PMID8539782.S2CID37077783.
Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, et al. (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library".Gene.200 (1–2):149–56.doi:10.1016/S0378-1119(97)00411-3.PMID9373149.
