A number of glutamine amidotransferases are under investigation to examine structure-function relationships for NH3 and glutamine utilization. Anthranilate synthetase from Serratia marcescens has been labeled with the glutamine analog 2-amino-4-oxo-5-chloropentanoic acid (chloroketone). A tryptic peptide containing the "glutamine site" has been isolated and sequence studies are in progress. Similar work is in progress on homogeneous anthranilate synthetase component II from Pseudomonas putida. E. coli glutamate synthase has been found to have activity with NH3 in addition to glutamine. The NH3-activity is dependent upon the state of the non heme iron and flavin. The glutamine activity was selectively inhibited with chloroketone. Studies are in progress to correlate the various activities with the two non identical protein chains. Immunological experiments are in progress to search for relatedness between anthranilate synthetase from various organisms and between other amidotransferases. The reaction of antibody with anthranilate synthetase will be studied in detail. Antibody reactions will be used to study subunit association and conformation changes.