Permeability to Sugars and Fatty Acids in Polytoma obtusum

SYNOPSIS. Whole cells of Polytoma obtusum do not utilize glucose or other hexoses, but cell-free extracts show glucokinase activity having a pH optimum at 8.5 and a Q₁₀ of 2.4 between 0–20°C. Lack of glucom utilization by whole cells reflects a permeability barrier to all sugars.
To determine whether inability of acetate-grown cells to utilize butyrate also denoted a permeability barrier, permeability to acetate and butyrate was studied in acetate- and butyrate-grown cells However, acetate-grown cells accumulated C-14 labeled butyrate against a concentration gradient. Therefore inability of acetate-grown cells to utilize butyrate does not denote a permeability barrier.
Acetate-kinase activity was consktently demonstrated in cell-free extracts of both acetate- and butyrate-grown cells. Butyrate kinase was consistently found only in butyrate-grown cells. However, the absence of buttymte kinase in acetate-grown cells cannot be claimed since occasionally butyrate kinase activity was demonstrated in extracts of acetate-grown cells.