Fatty acids binding to human serum albumin: Changes of reactivity and glycation level of Cysteine-34 free thiol group with methylglyoxal

Abstract

Fatty acids (FAs) binding to human serum albumin (HSA) could lead to the changes of Cys-34 thiol group accessibility and reactivity, i.e. its scavenger capacity and antioxidant property. The influence of saturated, mono and poly unsaturated, and fish oil FAs binding to HSA on the carbonylation level and the reactivity of HSA-SH and HSA modified with methylglyoxal (MG-HSA-SH) was investigated. Changes of thiol group reactivity were followed by determination of pseudo first order rate constant (k') for thiols reaction with 5,5'-dithiobis(2-nitrobenzoic acid). HSA changes were monitored using native PAG electrophoresis and fluorescence spectroscopy. For FA/HSA molar ratios screening, qTLC and GC were used. FAs increase thiol group carbonylation levels from 8% to 20%. The k' values obtained for FAs-free HSA-SH and FAs-free MG-HSA-SH are almost equal (7.5 x 10(-3) and 7.7 x 10(-3) resp.). Binding of all FAs amplify the reactivity (k' values from 14.6 x 10(-3) to 26.0 x 10(-3) s(-1)) of HSA-SH group for 2-3.5 times in the order: palmitic, docosahexaenoic, fish oil extract, stearic, oleic, myristic and eicosapentaenoic acid, due to HSA conformational changes. FAs-bound MG-HSA-SH samples follow that pattern, but their k' values (from 9.8 x 10(-3) to 14.3 x 10(-3) s(-1)) were lower compared to unmodified HSA due to additional conformation changes of HSA molecules during carbonylation. Carbonylation level and reactivity of Cys34 thiol group of unmodified and carbonylated HSA depend on type of FAs bound to HSA, which implies the possibility for modulation of -SH reactivity (scavenger capacity and antioxidant property) by FAs as a supplement.