The structural feature surrounding glycated lysine residues in human hemoglobin

Abstract

Complications derived from diabetes mellitus are caused by nonenzymatic protein glycation at the specific sites. LC/MS/MS was performed for the identification of the tryptic peptides of glycated hemoglobins using glyceraldehyde. After the identification of the glycation or non-glycation site, computer analysis of the structure surrounding the sites was carried out using PDB data (1BZ0). Five glycated lysine residues (Lys-16(α), -56(α), -8(β), -82(β), and -144(β)) and four non-glycated lysine residues (Lys-7(α), -40(α), -99(α), and -132(β)) were identified. The non-glycated lysine residues, Lys-7(α), -40(α), and -132(β), are most likely to form electrostatic interactions with the β

Insights into the Progression of Labile Hb A1cto Stable Hb A1cviaa Mechanistic Assessment of 2,3-Bisphosphoglycerate Facilitation of the Slow Nonenzymatic Glycation Process

“…the amine form of the Nterminal Val1 on the two β chains of Hb A) reacts with the electrophilic ring-opened form of glucose (structure 2). Moreover, several studies have shown that the rate of structure 3 formation is influenced by effector reagents such as inorganic phosphate and water serving as acids and/or bases [3,20,25,26].…”

“…A conservative cutoff distance of 5Å between potential reactive centers (distances between acidic protons and basic lone pairs of electrons; distances between nucleophilic and electrophilic atoms, etc.) was employed [19,20]. The reactive centers considered included reactive atoms (or lone pairs of electrons) on effector reagents (non covalently bound 2,3-BPG and/or water), the non covalently bound glucose, and resident amino acids in the Val1 pocket.…”

Potential roles of inorganic phosphate on the progression of initially bound glucopyranose toward the nonenzymatic glycation of human hemoglobin: Mechanistic diversity and impacts on site selectivity

“…Lys82 (also in the β-Val1 pocket) however, is predicted to undergo limited glycation which is consistent with in vivo glycation for HbA (Zhang et al, 2001; Delpierre et al, 2004). This is especially interesting because when glyceraldehyde is used as a glycation surrogate, Lys82 glycates readily (Nacharaju & Acharya, 1992; Ito et al, 2011). Glyceraldehyde does not undergo an NEG process, but instead follows a nonenzymatic covalent protein modification (NECPM) mechanism and cannot be compared directly to NEG (Rodnick et al, 2017).…”

“…Single substrate experiments utilized the complete HbA protein. Structures that were exothermic beyond the limit of −2.5 kcal/mol (the binding exothermicity of water) were analyzed, with a cutoff distance of 5Å established for effective reaction within protein pocket(s) (Bobadilla, Nino & Narasimhan, 2004; Ito et al, 2011). For concomitant binding studies, a glucopyranose was tether-docked in the pocket of interest and then a second substrate (i.e.…”

“…For HbA, a mechanism(s) for accelerating glycation has not been fully established. That said, most of the mechanisms that have been proposed place the Pi effect (here defined as glycation facilitation by Pi) at Amadori formation or later (Watkins et al, 1987; Gil et al, 1988; Kunika et al, 1989; Gil et al, 2002; Gil, Vasquez, Peña & Uzcategui, 2004; Gil, Salcedo & Romero, 2005; Ito, Nakahari & Yamamoto, 2011). Recently, Rodnick, Holman, Ropski, Huang & Swislocki (2017) posited that Pi plays multiple mechanistic roles within the pre-Amadori, early noncovalent stages of HbA glycation.…”