Non-enzymatic acetylation of human hemoglobins

Abstract

Chromatographically purified Hb F₀, Hb A₀ and Hb S₀ fractions were incubated with 70 μM [¹⁴C]acetyl-CoA for 3 h in 20 mM Tris-HCl, pH 7.6 and 8.6. The acid-precipitable radioactivity was monitored and the hemoglobins were separated by Biorex 70 chromatography. The pH dependence of acetylation showed an increase in acetylation with an increase in pH from 7.6 to 8.6, whereas an increase in ionic strength decreased acetylation. Incubation of Hb F₀ with [¹⁴C]acetyl-CoA resulted in modified hemoglobin and γ chains that co-chromatographed with Hb F_1c and γ_Ic chains, respectively. Acetylation of Hb A₀ and Hb S₀ produced minor hemoglobins whose chromatographic mobilities were slightly faster than those of Hb A_Ic and Hb S_Ic, respectively. Radioactivity peaks also appeared at the leading edges of the major hemoglobin zones as well, which indicates that, like non-enzymatic glycosylation, non-enzymatic acetylation of hemoglobins involves both specific and nonspecific reactions.