Glutamine Synthetase (GST)

  • Enzymes for Clinical Chemistry

The enzyme is useful for the determination of ammonia and ATP in clinical analysis.

Origin microorganism
Systematic name

L-Glutamate : ammonia ligase (ADP-forming)

EC Number 6.3.1.2
Reaction formula

ATP + L-Glutamate + NH3→→→ ADP + Orthophosphate + L-Glutamine

SPECIFICATION

Appearancelight yellow lyophilizate
Activity≧7 U/mg lyophilizate
Contaminantscatalase ≦0.5%
Stabilizersucrose
Storagebelow-20℃

PROPERTIES

Molecular weightca. 900 kDa (gel filtration)
Structure57 kDa (SDS-PAGE)
Isoelectric point6.5
Michaelis constant1.5×10-2M (L-glutamate)
1.3×10-4M (ammonia)
8.7×10-4M (ATP)
pH Optimum7.0
pH Stability6.5–9.5
Optimum temperature60℃
Thermal stabilitybelow 40℃
Stability (liquid form)stable at 20℃ for at least two weeks
Stability (powder form)stable at 37℃ for at least one month
Inhibitorsmethionine sulfoximine, carbamyl phosphate
ActivatorsMg2+,Mn2+
SpecificityL-glutamate (100), D-glutamate (0.8)
NH₃(100), NH₂OH (12)
ATP (100), GTP (2.5)

APPLICATIONS

The enzyme is useful for the determination of ammonia and ATP in clinical analysis.

REFERENCES

Ebner, E. et al., “Methods in Enzymology,” Vol. 17A, Academic Press, New York, 1970, pp. 910–922.

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