title: Thermostable alanine racemase of Bacillus stearothermophilus: subunit dissociation and unfolding.
abstract: The guanidine hydrochloride-induced subunit dissociation and unfolding of thermostable alanine racemase from Bacillus stearothermophilus have been studied by circular dichroism, fluorescence and absorption spectroscopies, and gel filtration. The overall process was found to be reversible: more than 75% of the original activity was recovered upon reduction of the denaturant concentration. In the range of 0.6 to 1.5 M guanidine hydrochloride, the dimeric enzyme was dissociated into a monomeric form, which was catalytically inactive. The monomeric enzyme appeared to bind the cofactor pyridoxal phosphate by a non-covalent linkage, although the native dimeric enzyme binds the cofactor through an aldimine Schiff base linkage. The monomer was mostly unfolded, with the transition occurring in the range of 1.8 to 2.2 M guanidine hydrochloride.
authors.affiliation: Laboratory of Microbial Biochemistry, Kyoto University.
authors.forename: H
authors.initials: H
authors.lastname: Toyama
authors.forename: N
authors.initials: N
authors.lastname: Esaki
authors.forename: T
authors.initials: T
authors.lastname: Yoshimura
authors.forename: K
authors.initials: K
authors.lastname: Tanizawa
authors.forename: K
authors.initials: K
authors.lastname: Soda
mesh_terms: D000411:Alanine Racemase / Q000378:metabolism*; D002850:Chromatography, Gel; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D011487:Protein Conformation; D011489:Protein Denaturation; D013057:Spectrum Analysis
chemical_list: D000411:Alanine Racemase