The combined effects of temperature and dilution on the activity and feedback inhibition of yeast aspartate transcarbamylase

Abstract

Dilution of a partially purified preparation of yeast aspartate transcarbamylase caused only a small loss of feedback inhibition and no change in specific activity when the assay was carried out at low temperature (0–10 °C). As the temperature of assay was increased, there was in the case of the dilute preparation a progressive loss of feedback inhibition coupled with a sharp increase in specific activity, reaching a level 400–500% that of the concentrated preparations. The data suggest that this is due to a dissociation into subunits possessing high aspartate transcarbamylase activity but lacking the regulatory site.