[en] The effect of pH on the stability and activity of rat liver RNA polymerases I (A) and II (B) has been studied. Both enzymes are irreversibly inactivated in buffer solutions below pH 5.0. Km values of the two enzymes are constant between pH 6.5 and 8.7 but a two -to three- fold increase is observed between pH 8.7 and 9.7. The Vmax versus pH profiles are bell-shaped curves indicating the participation of two ionizing groups with apparent pKa values of 6.5 and 9.8 for enzyme I and 6.7 and 9.9 for enzyme II. Both enzymes are inactivated by photooxidation in the presence of Rose Bengal. It is suggested that the above pKa corresponds to the imidazole of a histidine residue and a amino group of a lysine residue.
Disciplines :
Biochemistry, biophysics & molecular biology
Author, co-author :
Bull, P.
Martial, Joseph ; Université de Liège - ULiège > Département des sciences de la vie > GIGA-R : Biologie et génétique moléculaire
Téllez, R.
Venegas, A.
Valenzuela, P.
Language :
English
Title :
The pH dependence of rat liver RNA polymerases I and II.
