Functional analysis of recombinant human serum albumin domains for pharmaceutical applications.
OBJECTIVE
Functional analysis of the three recombinant human serum albumin (rHSA) domains and their potential as stand-alone proteins for use as drug delivery protein carriers.


METHODS
Protein structure was examined by fluorescence and CD spectroscopy. Ligand binding was estimated by ultrafiltration. Antioxidant activity was estimated by measuring the quenching of dihydrorhodamine 123. Esterase-like activity and enolase-like activity were estimated from the rate of hydrolysis of p-nitrophenyl acetate and conversion of dihydrotestosterone from the 3-keto to 3-enol form, respectively. The domains of human serum albumin (HSA) were radiolabeled with 111In to evaluate their pharmacokinetics.


RESULTS
The ligand binding ability of subsites Ia and Ib could not be detected in domain II. However, the binding of ligands to subsite Ic and site II were preserved in domain II and domain III, respectively. Domain III retained about 45% of its esterase-like activity, and weaker esterase-like activity was also observed in domain I. All domains showed low enolase-like activity in a pH 7.4 phosphate buffer, but domain II had higher activity in a pH 9.2 carbonate buffer. Domain I exhibited antioxidant activity comparable to that of rHSA. All three of the 111In-radiolabeled domains were rapidly eliminated from HSA, with high accumulation in the kidneys.


CONCLUSIONS
Domain I of HSA has great potential for further development as a drug delivery protein carrier, due to its favorable properties and the presence of a free cysteine residue.
Matsushita
Sadaharu
S
Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.
Isima
Yu
Y
Chuang
Victor Tuan Giam
VT
Watanabe
Hiroshi
H
Tanase
Sumio
S
Maruyama
Tomu
T
Otagiri
Masaki
M
D000465:Algorithms; D000818:Animals; D000975:Antioxidants / Q000737:chemistry; D001665:Binding Sites; D002021:Buffers; D002942:Circular Dichroism; D004337:Drug Carriers / Q000737:chemistry* / Q000493:pharmacokinetics; D016503:Drug Delivery Systems; D004950:Esterases / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D007205:Indium Radioisotopes; D008024:Ligands; D008297:Male; D051379:Mice; D010751:Phosphopyruvate Hydratase / Q000737:chemistry; D010843:Pichia / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins / Q000737:chemistry / Q000493:pharmacokinetics; D012709:Serum Albumin / Q000737:chemistry* / Q000493:pharmacokinetics; D013056:Spectrophotometry, Ultraviolet; D014018:Tissue Distribution
D000975:Antioxidants; D002021:Buffers; D004337:Drug Carriers; D007205:Indium Radioisotopes; D008024:Ligands; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D012709:Serum Albumin; D004950:Esterases; D010751:Phosphopyruvate Hydratase