Identification of Lys¹⁹⁰ as the primary binding site for pyridoxal 5′‐phosphate in human serum albumin

Abstract

The covalent binding of pyridoxal5'-phosphate (PLP) to human serum albumin (HSA) is important in the regulation of PLP metabolism. In plasma, PLP is bound to HSA at a single high-affinity and at two or more nonspecific sites. To characterize the primary PLP binding site, HSA was incubated with ['HIPLP, and the Schiff base linkage was reduced with potassium borohydride. Tryptic peptides were purified, and the major labeled peptide was sequenced. Amino acid analysis confirmed a homogeneous peptidc Leu-Asp-Glu-Lcu-Arp-As~GIu-Gly-Xaa-Als-Ser-Ser-Ala-Lys which corresponds to residues 182-195 of HSA. The data indicate that LyslYo is the primary PLP binding site. This Lys residue is distinct from other sites of covalent adduct formation; namely, the primary sites for nonenzymatic glycosylation (LysJz5) and acctyla.tion by aspirin (L~s'~~).Pyridoxal 5'.phosphate; Vitamin B6; Binding site; Albumin (human)

Physicochemical and Pharmacokinetic Characterization of Highly Potent Recombinant l-Methionine γ-Lyase Conjugated with Polyethylene Glycol as an Antitumor Agent

“…Because PLP bound to HSA is protected from hydrolysis by phosphorylases (43), HSA functions as a reservoir and mediates PLP transport to tissues. Binding sites for PLP in HSA have been identified as Lys 190 , which has a high affinity, and are composed of two or more nonspecific residues (39,44). We concluded that serum albumin detached PLP, which was coupled with the q-amino group at Lys 211 via a Schiff 's base of holoenzyme in vivo and in vitro.…”

Characterization of HKI-272 Covalent Binding to Human Serum Albumin

“…In addition, many covalent binding reports of exogenous ligands (drugs) to HSA occurred around this region or the same residue. For example, Lys190 was found to covalent bind to pyridoxal 5Ј-phosphate via Schiff base condensation (Bohney et al, 1992). Methylglyoxal, used as a covalent binding probe to interact with arginine residues of HSA, has been found to react with arginine 186 and 218, leading to the covalent binding (Ahmed et al, 2005).…”

Hapten–protein binding: from theory to practical application in the in vitro prediction of skin sensitization

“…the direct chemical modification of the protein residues via specific chemical reactions. Several key HSA residues have been shown to be selectively and covalently modified by chemicals, such as Cys 34 (38) Lys 190 (39), Lys 199 (28, 40, 41), His 9, His 146, His 338 (42) and Arg 410 (22). HSA has 17 pairs of cysteines involved in disulfide linkages and only 1 free Cys residue (Cys 34).…”