Reduction and S-nitrosation of the neuropeptide oxytocin: implications for its biological function.
Oxytocin (OT; Cys-Tyr-Ile-Gln-Asn-Cys-Pro-leu-Gly), a posterior pituitary peptide hormone, is characterized by a Cys1-Cys6 disulfide bond in its stable, isolated state. This paper describes a simple, one-step method for the production of OT in its reduced, dithiol form (OT dithiol), free of reducing agent. The effects of temperature, pH, and metal-ion chelators on the autoxidation of OT dithiol were examined to establish if this form is likely to persist under biological conditions. It was found that OT dithiol has a half-life of 1.8h with respect to reformation of OT disulfide at 37 degrees C and pH 6.9 in the presence of the copper chelators, DTPA and neocuproine. S-Nitrosation of OT dithiol by acidified nitrite at pH 3.0 was examined by absorption spectroscopy and HPLC-UV-MS, which revealed that both singly and doubly S-nitrosated OT are formed. These results suggest novel chemical aspects to OT signaling, the biological implications of which are discussed here.
Roy
Jean-François
JF
Department of Chemistry and Biochemistry, Centre for Biological Applications of Mass Spectrometry, Concordia University, 7141 Sherbrooke Street W., Montreal, Que., Canada.
Chrétien
Michelle N
MN
Woodside
Barbara
B
English
Ann M
AM
D003545:Cysteine / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry; D009479:Neuropeptides / Q000737:chemistry*; D009573:Nitrites / Q000737:chemistry*; D010084:Oxidation-Reduction; D010121:Oxytocin / Q000737:chemistry* / Q000502:physiology; D013438:Sulfhydryl Compounds
D004220:Disulfides; D009479:Neuropeptides; D009573:Nitrites; D013438:Sulfhydryl Compounds; D010121:Oxytocin; D003545:Cysteine