Relative Roles of Albumin and Ceruloplasmin in the Formation of Homocystine, Homocysteine-Cysteine-mixed Disulfide, and Cystine in Circulation

Shantanu Sengupta, Charles Wehbe, Alana K. Majors, Michael E Ketterer, Patricia M. DiBello, Donald W. Jacobsen

Research output: Contribution to journalArticle

108 Citations (Scopus)

Abstract

Disulfide forms of homocysteine account for >98% of total homocysteine in plasma from healthy individuals. We recently reported that homocysteine reacts with albumin-Cys34-S-S-cysteine to form homocysteine-cysteine mixed disulfide and albumin-Cys34 thiolate anion. The latter then reacts with homocystine or homocysteine-cysteine mixed disulfide to form albumin-bound homocysteine (Sengupta, S., Chen, H., Togawa, T., DiBello, P. M., Majors, A. K., Büdy, B., Ketterer, M. E., and Jacobsen, D. W. (2001) J. Biol. Chem. 276, 30111-30117). We now extend these studies to show that human albumin, but not ceruloplasmin, mediates the conversion of homocysteine to its low molecular weight disulfide forms (homocystine and homocysteine-cysteine mixed disulfide) by thiol/disulfide exchange reactions. Only a small fraction of homocystine is formed by an oxidative process in which copper bound to albumin, but not ceruloplasmin, mediates the reaction. When copper is removed from albumin by chelation, the overall conversion of homocysteine to its disulfide forms is reduced by only 20%. Ceruloplasmin was an ineffective catalyst of homocysteine oxidation, and immunoprecipitation of ceruloplasmin from human plasma did not inhibit the capacity of plasma to mediate the conversion of homocysteine to its disulfide forms. In contrast, ceruloplasmin was a highly efficient catalyst for the oxidation of cysteine and cysteinylglycine to cystine and bis(-S-cysteinylglycine), respectively. However, when thiols (cysteine and homocysteine) that are disulfide-bonded to albumin-Cys34 are removed by treatment with dithiothreitol to form albumin-Cys34-SH (mercaptalbumin), the conversion of homocysteine to its disulfide forms is completely blocked. In conclusion, albumin mediates the formation of disulfide forms of homocysteine by thiol/disulfide exchange, whereas ceruloplasmin converts cysteine to cystine by copper-dependent autooxidation.

Original languageEnglish (US)
Pages (from-to)46896-46904
Number of pages9
JournalJournal of Biological Chemistry
Volume276
Issue number50
DOIs
StatePublished - Dec 14 2001
Externally publishedYes

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Homocystine
Ceruloplasmin
Cystine
Homocysteine
Albumins
Disulfides
cysteinylglycine
Cysteine
Sulfhydryl Compounds
Copper
cysteinylhomocysteine mixed disulfide
Plasma (human)
Plasmas
Oxidation
Catalysts
Dithiothreitol
Chelation
Immunoprecipitation
Anions

ASJC Scopus subject areas

  • Biochemistry

Cite this

Relative Roles of Albumin and Ceruloplasmin in the Formation of Homocystine, Homocysteine-Cysteine-mixed Disulfide, and Cystine in Circulation. / Sengupta, Shantanu; Wehbe, Charles; Majors, Alana K.; Ketterer, Michael E; DiBello, Patricia M.; Jacobsen, Donald W.

In: Journal of Biological Chemistry, Vol. 276, No. 50, 14.12.2001, p. 46896-46904.

Research output: Contribution to journalArticle

Sengupta, Shantanu ; Wehbe, Charles ; Majors, Alana K. ; Ketterer, Michael E ; DiBello, Patricia M. ; Jacobsen, Donald W. / Relative Roles of Albumin and Ceruloplasmin in the Formation of Homocystine, Homocysteine-Cysteine-mixed Disulfide, and Cystine in Circulation. In: Journal of Biological Chemistry. 2001 ; Vol. 276, No. 50. pp. 46896-46904.
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abstract = "Disulfide forms of homocysteine account for >98{\%} of total homocysteine in plasma from healthy individuals. We recently reported that homocysteine reacts with albumin-Cys34-S-S-cysteine to form homocysteine-cysteine mixed disulfide and albumin-Cys34 thiolate anion. The latter then reacts with homocystine or homocysteine-cysteine mixed disulfide to form albumin-bound homocysteine (Sengupta, S., Chen, H., Togawa, T., DiBello, P. M., Majors, A. K., B{\"u}dy, B., Ketterer, M. E., and Jacobsen, D. W. (2001) J. Biol. Chem. 276, 30111-30117). We now extend these studies to show that human albumin, but not ceruloplasmin, mediates the conversion of homocysteine to its low molecular weight disulfide forms (homocystine and homocysteine-cysteine mixed disulfide) by thiol/disulfide exchange reactions. Only a small fraction of homocystine is formed by an oxidative process in which copper bound to albumin, but not ceruloplasmin, mediates the reaction. When copper is removed from albumin by chelation, the overall conversion of homocysteine to its disulfide forms is reduced by only 20{\%}. Ceruloplasmin was an ineffective catalyst of homocysteine oxidation, and immunoprecipitation of ceruloplasmin from human plasma did not inhibit the capacity of plasma to mediate the conversion of homocysteine to its disulfide forms. In contrast, ceruloplasmin was a highly efficient catalyst for the oxidation of cysteine and cysteinylglycine to cystine and bis(-S-cysteinylglycine), respectively. However, when thiols (cysteine and homocysteine) that are disulfide-bonded to albumin-Cys34 are removed by treatment with dithiothreitol to form albumin-Cys34-SH (mercaptalbumin), the conversion of homocysteine to its disulfide forms is completely blocked. In conclusion, albumin mediates the formation of disulfide forms of homocysteine by thiol/disulfide exchange, whereas ceruloplasmin converts cysteine to cystine by copper-dependent autooxidation.",
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AU - DiBello, Patricia M.

AU - Jacobsen, Donald W.

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N2 - Disulfide forms of homocysteine account for >98% of total homocysteine in plasma from healthy individuals. We recently reported that homocysteine reacts with albumin-Cys34-S-S-cysteine to form homocysteine-cysteine mixed disulfide and albumin-Cys34 thiolate anion. The latter then reacts with homocystine or homocysteine-cysteine mixed disulfide to form albumin-bound homocysteine (Sengupta, S., Chen, H., Togawa, T., DiBello, P. M., Majors, A. K., Büdy, B., Ketterer, M. E., and Jacobsen, D. W. (2001) J. Biol. Chem. 276, 30111-30117). We now extend these studies to show that human albumin, but not ceruloplasmin, mediates the conversion of homocysteine to its low molecular weight disulfide forms (homocystine and homocysteine-cysteine mixed disulfide) by thiol/disulfide exchange reactions. Only a small fraction of homocystine is formed by an oxidative process in which copper bound to albumin, but not ceruloplasmin, mediates the reaction. When copper is removed from albumin by chelation, the overall conversion of homocysteine to its disulfide forms is reduced by only 20%. Ceruloplasmin was an ineffective catalyst of homocysteine oxidation, and immunoprecipitation of ceruloplasmin from human plasma did not inhibit the capacity of plasma to mediate the conversion of homocysteine to its disulfide forms. In contrast, ceruloplasmin was a highly efficient catalyst for the oxidation of cysteine and cysteinylglycine to cystine and bis(-S-cysteinylglycine), respectively. However, when thiols (cysteine and homocysteine) that are disulfide-bonded to albumin-Cys34 are removed by treatment with dithiothreitol to form albumin-Cys34-SH (mercaptalbumin), the conversion of homocysteine to its disulfide forms is completely blocked. In conclusion, albumin mediates the formation of disulfide forms of homocysteine by thiol/disulfide exchange, whereas ceruloplasmin converts cysteine to cystine by copper-dependent autooxidation.

AB - Disulfide forms of homocysteine account for >98% of total homocysteine in plasma from healthy individuals. We recently reported that homocysteine reacts with albumin-Cys34-S-S-cysteine to form homocysteine-cysteine mixed disulfide and albumin-Cys34 thiolate anion. The latter then reacts with homocystine or homocysteine-cysteine mixed disulfide to form albumin-bound homocysteine (Sengupta, S., Chen, H., Togawa, T., DiBello, P. M., Majors, A. K., Büdy, B., Ketterer, M. E., and Jacobsen, D. W. (2001) J. Biol. Chem. 276, 30111-30117). We now extend these studies to show that human albumin, but not ceruloplasmin, mediates the conversion of homocysteine to its low molecular weight disulfide forms (homocystine and homocysteine-cysteine mixed disulfide) by thiol/disulfide exchange reactions. Only a small fraction of homocystine is formed by an oxidative process in which copper bound to albumin, but not ceruloplasmin, mediates the reaction. When copper is removed from albumin by chelation, the overall conversion of homocysteine to its disulfide forms is reduced by only 20%. Ceruloplasmin was an ineffective catalyst of homocysteine oxidation, and immunoprecipitation of ceruloplasmin from human plasma did not inhibit the capacity of plasma to mediate the conversion of homocysteine to its disulfide forms. In contrast, ceruloplasmin was a highly efficient catalyst for the oxidation of cysteine and cysteinylglycine to cystine and bis(-S-cysteinylglycine), respectively. However, when thiols (cysteine and homocysteine) that are disulfide-bonded to albumin-Cys34 are removed by treatment with dithiothreitol to form albumin-Cys34-SH (mercaptalbumin), the conversion of homocysteine to its disulfide forms is completely blocked. In conclusion, albumin mediates the formation of disulfide forms of homocysteine by thiol/disulfide exchange, whereas ceruloplasmin converts cysteine to cystine by copper-dependent autooxidation.

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