title: [Secondary structure and functional groups of the active center of glutamine synthetase of pea chloroplasts].
abstract: The circular dichroism spectra of glutamine synthetase (EC 6.3.1.2) from pea chloroplasts were recorded. Based on these spectra the percentage of alpha-helix sites, beta-structures, beta-bends and disordered sites of the polypeptide chain was calculated and was found equal to 23, 57, 1 and 23%, respectively. Data from protein photooxidation in the presence of methylene blue and the type of pH-dependence of pKm suggest that glutamate binding takes place on the imidazole ring of the histidine molecule. The inhibition of native glutamine synthetase by p-chloromercurybenzoate and the presence of free SH-groups in the enzyme molecule (approximately two SH-groups per monomer) suggest that these groups are the functional groups of the enzyme active center.
mesh_terms: D001665:Binding Sites; D002736:Chloroplasts / Q000201:enzymology*; D002942:Circular Dichroism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D007700:Kinetics; D010944:Plants / Q000201:enzymology; D011487:Protein Conformation
chemical_list: D005974:Glutamate-Ammonia Ligase
vernacular_title: Vtorichnaia struktura i funktsional'nye gruppy aktivnogo tsentra glutaminsintetazy khloroplastov gorokha.