In Vitro Activation of a Galactosyl Transferase Involved in the Osmotic Regulation of Ochromonas

Publisher Website
Google Scholar
Abstract
Osmotic regulation in the flagellate O. malhamensis Pringsheim was mainly mediated by fluctuations in the pool size of .alpha.-galactosyl-(1 .fwdarw. 1)-glycerol (isofloridoside). A regulated key enzyme of isofloridoside metabolism was the galactosyl transferase producing isofloridoside phosphate. The activity of this enzyme in crude extracts can be increased 5-20-fold by incubation at pH 6. The activation occurs in a reaction with a Q10 of 1.5-3 and is dependent on time and pH value. Inactivation of the activated form of the enzyme is also time-dependent, and is minimal at the pH value at which activation is optimal. The data suggest a regulation of the enzyme by chemical modification due to the action of auxiliary enzymes.