Stopped flow kinetic studies of adenosine triphosphate phosphoribosyl transferase, the first enzyme in the histidine biosynthesis of Escherichia coli

Abstract

1. Stopped flow kinetic studies of ATP phosphoribosyl transferase (EC 2.4.2.17) from Escherichia coli showed that high protein concentration and elevated temperature do not give a drastic reduction of the transferase activity when measured before inhibitory amounts of PRibATP (product) has accumulated. 2. A small and slow increase in activity follows a reduction of the protein concentration showing a slow dissociation of the enzyme from an inactive to an active species. 3. By lowering the concentration of the inhibitor histidine, a fairly slow increase in activity is observed indicating a dissociation of the enzyme. 4. AMP and histidine together give a strong inhibition of the activity, while AMP alone stimulates the enzyme activity.