Regulation of glutamine synthetase activity by phosphorylation instead of by adenylylation.
o-Phosphotyrosyl glutamine synthetase (P-GS) was isolated from highly adenylated glutamine synthetase (AMP-GS) purified from Mycobacterium phlei, by treatment with micrococcal nuclease. The physical characteristics of P-GS were quite similar to those of AMP-GS except for the UV-absorption spectrum. In either Mg2+- or Mn2+-dependent biosynthetic reactions, the kinetic properties, such as optimum pH, Vmax, and apparent Km for each of three substrates of P-GS, were found to be in good agreement with those of AMP-GS. The biosynthetic activity of P-GS was markedly increased after treatment with alkaline phosphatase similarly as in the deadenylylation of AMP-GS by snake venom phosphodiesterase treatment. These results revealed that repression of glutamine synthetase activity simply requires the phosphorylation of the tyrosyl residue, without recourse to adenylylation.
D000225:Adenine / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008836:Micrococcal Nuclease / Q000378:metabolism; D010766:Phosphorylation
D008836:Micrococcal Nuclease; D005974:Glutamate-Ammonia Ligase; D000225:Adenine