The enzyme, characterized from the bacterium Streptomyces viridochromogenes, participates in the biosynthesis of the herbicide antibiotic bialaphos. The enzyme from the bacterium Kitasatospora phosalacinea participates in the biosynthesis of the related compound phosalacine. Both compounds contain the nonproteinogenic amino acid L-phosphinothricin that acts as a potent inhibitor of EC 6.3.1.2, glutamine synthetase.