Influence of glycerol and other polyhydric alcohols on the quaternary structure of an oligomeric protein

Abstract

Dissociation of tetrameric l-asparaginase from Escherichia coli B was examined in the presence of urea containing one of the following polyhydric alcohols: ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, erythritol, arabitol, adonitol, mannitol, sorbitol, inositol, glucose, sucrose, and polyethylene glycol. Low concentrations of these compounds accelerate the rate of subunit dissociation, and, with the exception of the propanediols and polyethylene glycol, higher concentrations decrease the rate at which the oligomeric enzyme dissociates. The specific concentration at which this transition occurs is related to the length of the carbon chain of the polyhydric alcohols and to the steric configuration of the hydroxyl groups about the asymmetric carbon atoms. In addition, the rate at which the oligomeric enzyme dissociates decreases as the number of hydroxymethyl groups per molecule polyol increases and reaches a maximum with the six carbon members. Low concentrations (1% by volume) of methanol, ethanol, ethylene glycol, propylene glycol, or glycerol contained in the renaturation buffer slightly accelerate the rate of reassembly of denatured subunits. The rate at which reassociation to the tetramer occurs also increases as the number of hydroxymethyl groups per molecule of polyhydric alcohol increases.