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Bound homocysteine, cysteine, and cysteinylglycine distribution between albumin and globulins.
Clin Chem. 2006 Dec; 52(12):2258-64.CC

Abstract

BACKGROUND

Major portions of homocysteine (Hcy), cysteine (Cys), cysteinylglycine (CysGly), and glutathione in serum are covalently bound to proteins via disulfides. Albumin has been considered the dominant binding protein.

METHODS

Pooled serum and plasma from healthy adults were fractionated into albumin and globulins by affinity columns. Content of Hcy, Cys, CysGly, and glutathione was determined for serum and plasma fractions and purified proteins by an HPLC method before and after incubation with excess CysGly, Hcy, or glutathione

RESULTS

Of protein-bound amino acids in pooled serum, 12% of Hcy, 21% of Cys, and 33% of CysGly were bound to globulins, with the remainder bound to albumin. Slightly higher proportions were bound to globulins in pooled plasma. Globulins had approximately 16% of total exchangeable disulfide and thiol groups in serum based on results of loading with CysGly. These results agree with expected abundance of unpaired Cys residues in globulins relative to albumin. Significant amounts of disulfide-linked amino acids were detected for HDL and alpha1-acid glycoprotein but not for transferrin. Exchange of disulfide-linked amino acids on exposure to excess Hcy or glutathione was much faster for albumin than for alpha1-acid glycoprotein.

CONCLUSIONS

Approximately 10%-30%, of protein-bound Hcy, Cys, and CysGly are disulfide-linked to globulins. Amino acids disulfide-linked to albumin are rapidly exchangeable, while exchange of disulfide-linked amino acids from globulins, such as alpha1-acid glycoprotein, is much slower. Consequently, the pools of Hcy, Cys, and CysGly bound to albumin and globulin may represent kinetically and functionally distinct pools. Plasma concentrations of total Hcy and Cys, which are dominated by albumin-bound pools, may not reflect the abundance of functionally significant modifications of globulins.

Authors+Show Affiliations

Department of Laboratory Medicine, Warren Magnuson Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA. ghortin@mail.cc.nih.govNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Intramural

Language

eng

PubMed ID

17068168

Citation

Hortin, Glen L., et al. "Bound Homocysteine, Cysteine, and Cysteinylglycine Distribution Between Albumin and Globulins." Clinical Chemistry, vol. 52, no. 12, 2006, pp. 2258-64.
Hortin GL, Seam N, Hoehn GT. Bound homocysteine, cysteine, and cysteinylglycine distribution between albumin and globulins. Clin Chem. 2006;52(12):2258-64.
Hortin, G. L., Seam, N., & Hoehn, G. T. (2006). Bound homocysteine, cysteine, and cysteinylglycine distribution between albumin and globulins. Clinical Chemistry, 52(12), 2258-64.
Hortin GL, Seam N, Hoehn GT. Bound Homocysteine, Cysteine, and Cysteinylglycine Distribution Between Albumin and Globulins. Clin Chem. 2006;52(12):2258-64. PubMed PMID: 17068168.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Bound homocysteine, cysteine, and cysteinylglycine distribution between albumin and globulins. AU - Hortin,Glen L, AU - Seam,Nitin, AU - Hoehn,Gerard T, Y1 - 2006/10/26/ PY - 2006/10/28/pubmed PY - 2007/2/3/medline PY - 2006/10/28/entrez SP - 2258 EP - 64 JF - Clinical chemistry JO - Clin Chem VL - 52 IS - 12 N2 - BACKGROUND: Major portions of homocysteine (Hcy), cysteine (Cys), cysteinylglycine (CysGly), and glutathione in serum are covalently bound to proteins via disulfides. Albumin has been considered the dominant binding protein. METHODS: Pooled serum and plasma from healthy adults were fractionated into albumin and globulins by affinity columns. Content of Hcy, Cys, CysGly, and glutathione was determined for serum and plasma fractions and purified proteins by an HPLC method before and after incubation with excess CysGly, Hcy, or glutathione RESULTS: Of protein-bound amino acids in pooled serum, 12% of Hcy, 21% of Cys, and 33% of CysGly were bound to globulins, with the remainder bound to albumin. Slightly higher proportions were bound to globulins in pooled plasma. Globulins had approximately 16% of total exchangeable disulfide and thiol groups in serum based on results of loading with CysGly. These results agree with expected abundance of unpaired Cys residues in globulins relative to albumin. Significant amounts of disulfide-linked amino acids were detected for HDL and alpha1-acid glycoprotein but not for transferrin. Exchange of disulfide-linked amino acids on exposure to excess Hcy or glutathione was much faster for albumin than for alpha1-acid glycoprotein. CONCLUSIONS: Approximately 10%-30%, of protein-bound Hcy, Cys, and CysGly are disulfide-linked to globulins. Amino acids disulfide-linked to albumin are rapidly exchangeable, while exchange of disulfide-linked amino acids from globulins, such as alpha1-acid glycoprotein, is much slower. Consequently, the pools of Hcy, Cys, and CysGly bound to albumin and globulin may represent kinetically and functionally distinct pools. Plasma concentrations of total Hcy and Cys, which are dominated by albumin-bound pools, may not reflect the abundance of functionally significant modifications of globulins. SN - 0009-9147 UR - https://www.unboundmedicine.com/medline/citation/17068168/Bound_homocysteine_cysteine_and_cysteinylglycine_distribution_between_albumin_and_globulins_ L2 - https://academic.oup.com/clinchem/article-lookup/doi/10.1373/clinchem.2006.074302 DB - PRIME DP - Unbound Medicine ER -