Chloride ion as a modifier of 2′,3′-Cyclic phosphodiesterase purified from halophilic Vibrio alginolyticus

Abstract

1. 1.2′,3′-Cyclic phosphodiesterase having 3′-nucleotidase activity (which hydrolyzes ribonucleoside 2′,3′-cyclic phosphates, ribonucleoside 3′-phosphates and di- p-nitrophenyl phosphate) was purified 2000-fold from slightly halophilic Vibrio alginolyticus. The activities for these substrates were inseparable by any of the purification steps used. 2. 2.This enzyme had the maximal activity on all of the substrates in the pH ranges from 7.6 to 8.6 and possessed several properties different from those reported (by others) for Escherichia coli and Proteus mirabilis. 3. 3.Chloride ion acted as an activator for the hydrolysis of 3′-ribonucleotides and di- p-nitrophenyl phosphate; however, it acted as an inhibitor for the cyclic phosphodiesterase activity. The kinetic results of the effect of the chloride ion on the hydrolyses of these substrates were well explained in terms of the equation described by Frieden on the single substrate-single modifier case. From these, it was assumed that the chloride ion inversely modifies the two activities in the same protein molecule by affecting the configurational changes in the enzyme structure so as to activate the 3′-nucleotidase and to inhibit the cyclic phosphodiesterase.