Glutamine synthetase from the pumpkin leaf cytosol

Abstract

Glutamine synthetase (l-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2) from pumpkin leaf cytosol is an oligomer that consists of eight identical monomers. The enzyme has a partial specific volume of 0.720 ml/g. The pH optimum in the presence of Mg²⁺ is 7.2. It is shown by means of electron microscopy that the enzyme consists of elongated monomers, which are arranged with point 42 symmetry at the vertices of two squares. These squares are twisted about the 4-fold axis at 40° relative to each other.