Purification and properties of glutaminase and asparaginase from a pseudomonad: II. Substrate specificity, kinetics, activation, and inhibition

Abstract

Various properties have been studied of a highly purified enzyme preparation from a strain of Pseudomonas which has both glutaminase and asparaginase activities. The enzyme preparation is highly specific for l-glutamine and l-asparagine. d-Asparagine has about 20% of the activity of the l-enantiomorph. The glutaminase activity of the enzyme preparation is activated by certain divalent anions and is inhibited by monovalent anions. The asparaginase activity is greatly increased by cyanide, thiocyanate, and nitrate ions. Both enzyme activities are increased by a variety of divalent cations. Fe ++ and Hg ++ are strongly inhibitory. The enzyme preparation shows good glutaminase activity over the pH range of 5–8, with an optimum value at pH 6.6. The asparaginase activity is highest at pH 8.2. The glutaminase activity is strongly inhibited by all phthalein dyes and moderately by flavianic acid and atabrine; the asparaginase activity is strongly inhibited only by bromocresol green. Ammonia and d- and l-glutamic acids are competitive inhibitors of the glutaminase activity; ammonia and l-aspartic acid have no effect on the asparaginase activity.