Studies in biochemical adaptation. Some aspects of galactozymase production by yeast in relation to the ‘mass action’ theory of enzyme adaptation

Abstract

Predictions made from the "mass action" theory of enzyme adaptation (see preceding 2 abstracts) were tested in expts. on the adaptation of yeast cells to the fermentation of galactose. The rate of adaptation in a given concn. of galactose was found to be either linear or exponentially increasing. In no instance was a linear rate found when there was an increase in cell mass during adaptation. The initial rate of adaptation was independent of the concn. of galactose over the tested range of 3-8%. When there was no restriction of material for the building of the enzyme, the amt. of galactozymase formed was linearly related to the concn. of galactose. When there was such a restriction, there was a decreasing increment of enzyme with increasing concn. and the total amt. of enzyme formed was less. The relative amts. of galactozymase and maltozymase formed in the presence of both sugars were determined by the relative amts. of galactose and maltose present. These results, and others reported in the literature, are quantitatively in agreement with the predictions made from the theory.