Determination of the binding properties of the uremic toxin phenylacetic acid to human serum albumin

• Published in: Biochimie 2016-06, Vol.125, p.53-58
• Main Authors: Saldanha, Juliana F., Yi, Dan, Stockler-Pinto, Milena B., Soula, Hédi A., Chambert, Stéphane, Fouque, Denis, Mafra, Denise, Soulage, Christophe O.
• Format: Article
• Language: English
• Subjects: Cell Line; Chronic kidney disease; Human serum albumin; Humans; Life Sciences; Phenylacetates - chemistry; Phenylacetic acid; Protein Binding; Protein Domains; Renal Insufficiency, Chronic - blood; Serum Albumin - chemistry; Serum Albumin - metabolism; Uremic syndrome; Uremic toxin
• ISSN: 0300-9084; 1638-6183
• DOI: 10.1016/j.biochi.2016.03.002

Uremic toxins are compounds normally excreted in urine that accumulate in patients with chronic kidney disease as a result of decreased renal clearance. Phenylacetic acid (PAA) has been identified as a new protein bound uremic toxin. The purpose of this study was to investigate in vitro the interaction between PAA and human serum albumin (HSA) at physiological and pathological concentrations. We used ultrafiltration to show that there is a single high-affinity binding site for PAA on HSA, with a binding constant on the order of 3.4 × 104 M−1 and a maximal stoichiometry of 1.61 mol per mole. The PAA, at the concentration reported in end-stage renal patients, was 26% bound to albumin. Fluorescent probe competition experiments demonstrated that PAA did not bind to Sudlow's site I (in subdomain IIA) and only weakly bind to Sudlow's site II (in subdomain IIIA). The PAA showed no competition with other protein-bound uremic toxins such as p-cresyl-sulfate or indoxyl sulfate for binding to serum albumin. Our results provide evidence that human serum albumin can act as carrier protein for phenylacetic acid. •Phenylacetic acid (PAA) is an uremic toxins that accumulates in patients with chronic kidney disease.•Human serum albumin (HSA) is a protein carrier for PAA.•There is one single high-affinity binding site for PAA on HSA.•PAA does not compete with other hydrophobic uremic toxins such as p-cresyl-sulfate or indoxyl sulfate for binding to HSA.