Volume 29, Issue 6 pp. 759-771

Investigation of non-covalent complexes of glutathione with common amino acids by electrospray ionization mass spectrometry1

Zhao-yun DAI

Zhao-yun DAI

Department of Infectious Disease, Huadong Hospital, Shanghai 200040, China

Both authors contributed equally to this work.

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Yan-qiu CHU

Yan-qiu CHU

Department of Chemistry, Fudan University, Shanghai 200433, China

Both authors contributed equally to this work.

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Bo WU

Bo WU

Department of Chemistry, Fudan University, Shanghai 200433, China

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Liang WU

Liang WU

Department of Chemistry, Fudan University, Shanghai 200433, China

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Chuan-fan DING

Corresponding Author

Chuan-fan DING

Department of Chemistry, Fudan University, Shanghai 200433, China

Correspondence to Prof Chuan-fan DING. Phn 86-21-6510-5204. Fax 86-21-5566-4549. E-mail [email protected]; [email protected]Search for more papers by this author
First published: 03 June 2008
Citations: 3
1

Project supported by the National Natural Science Foundation of China (No 20473020).

Abstract

Aim: To study the non-covalent interaction between glutathione and common amino acids. Methods: A stoichiometry of glutathione and common amino acids were mixed to reach the equilibrium, and then the mixed solution was investigated by electrospray ionization mass spectrometry (ESI–MS). The binding of the complexes was further examined by collision-induced dissociation (CID) in a tandem mass spectrometer as well as UV spectroscopy. To avoid distinct ionization efficiency discrepancy and signal suppression in the ESI-MS measurements, the interaction between glutathione (GSH) and glutamate (Glu) was quantitatively evaluated. The total concentrations and series of m/z of peak intensities for glu-tathione and amino acids could be achieved, respectively. Due to the existence of some oligomeric species arising from glutathione or amino acids, an improved calculation formula was proposed to calculate the dissociation constants of glutathione binding to amino acids. Results: The ESI mass spectra revealed that glutathione could interact easily with Met, Phe, Tyr, Ser, or Ile to form non-cova-lent complexes. The binding of the complexes was further confirmed by CID experiments in a tandem mass spectrometer as well as UV spectroscopy. Moreover, an improved calculation formula was successfully applied to determine the dissociation constants of glutathione binding to Glu, His, or Gln. Finally, a possible formation mechanism for the complexes of glutathione with amino acids was proposed. Conclusion: The reduced polypeptide γ-glutathione can interact with each of 8 common amino acids, including Glu, His, and Gln to form non-covalent complexes with different affinity.

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