Collect. Czech. Chem. Commun. 1988, 53, 411-422

Mechanism of denaturation of human serum albumin by urea

Josef Chmelíka, Pavel Anzenbacherb, Jitka Chmelíkováa, Milada Matějčkovác and Vítěz Kalousc

a Institute of Analytical Chemistry, Czechoslovak Academy of Sciences, 611 42 Brno
b Department of Biochemistry
c Department of Physical Chemistry, Charles University, 128 40 Prague 2


The mechanism of denaturation of human serum albumin by urea was examined by polarography, polarimetry, circular dichroism, UV-spectrophotometry, gel chromatography, and polyacrylamide gel electrophoresis. Comparison of the results obtained by these methods shows that this reaction is a complex process which cannot be described by a two-state denaturation model. It has been demonstrated that the different states which denaturation produces arise under different denaturation conditions. The different behavior of various species of human serum albumin (monomer, mercaptalbumin and nonmercaptalbumin) during denaturation by urea was examined. As a result the following probable denaturation scheme was proposed: The denaturation of human serum albumin by urea is regarded as a stepwise process involving one stable intermediary product at least ( demonstrated electrophoretically). After the rapid initial change of the ordered helical structure extensive hydrophobic domains of the molecule remain folded. Cystine residues are gradually liberated from these domains. Denaturated mercaptalbumin has the conformation of a random coil in which the pairing of native disulfide bonds has been altered because of SH-S-S interchange reactions; in contrast native disulfide bonds are retained in nonmercaptalbumin.