Glutamine Synthetase (GST)

  • Enzymes for Clinical Chemistry

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

Origin microorganism
Lineage name

L-Glutamate : ammonia ligase (ADP-forming)

EC Number 6.3.1.2
Reaction formula

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

SPECIFICATION

Appearance light yellow lyophilizate
Activity ≧7 U/mg lyophilizate
Contaminants catalase ≦0.5%
Stabilizer sucrose
Storage below-20℃

PROPERTIES

Molecular weight ca. 900 kDa (gel filtration)
Structure 57 kDa (SDS-PAGE)
Isoelectric point 6.5
Michaelis constant 1.5×10-2M (L-glutamate)
1.3×10-4M (ammonia)
8.7×10-4M (ATP)
pH Optimum 7.0
pH Stability 6.5–9.5
Optimum temperature 60℃
Thermal stability below 40℃
Stability (liquid form) stable at 20℃ for at least two weeks
Stability (powder form) stable at 37℃ for at least one month
Inhibitors methionine sulfoximine, carbamyl phosphate
Activators Mg2+,Mn2+
Specificity L-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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