Glutathione Synthetase of Aspergillus niger: Structural Properties of the Enzyme in Prokaryotes and Eukaryotes

Glutathione synthetase isolated from a mold, Aspergillus niger, had a molecular weight of 110,000 and consisted of two apparently identical subunits, each with a molecular weight of 55,000. The enzyme was most active at pH 8.5. It specifically utilized glycine and ATP, and required Mg^{2 +} or Mn^{2 +} for its catalytic function. A comparison of glutathione synthetases from various sources indicated that the enzyme of eukaryotes (mammals, molds and yeasts) differ from those of prokaryotes {Escherichia coli B and Proteus mirabilis) in molecular structure, although the enzymes from both types of organisms contain an active site thiol and catalyze the same reaction.