Electronic Resource
Oxford, UK
:
Blackwell Publishing Ltd
Physiologia plantarum
61 (1984), S. 0
ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
γ-Glutamyl-transpeptidase activity (EC 2.3.2.2) was found in ammonium sulfate precipitates of extracts from cultured cells of Nicotiana tabacum L. var. Samsun. Specific activity up to 3.2 nmol (mg protein)−1 min−1 was achieved, using the artificial substrate γ-glutamyl-p-nitroanilide (Km 0.6 mM) instead of glutathione. Optimal enzyme activity was obtained at pH 8.0–8.5 and 45°C. The enzyme reaction was inhibited competitively by γ-glutamyl analogs (6-diazo-5-oxo-L-norleucine: Ki 0.76 μM; L-azaserine: Ki 0.23 mM) or the inorganic ion m-periodate (Ki 0.43 mM). Cell fractionation and in vivo experiments revealed that 77% of the γ-glutamyl-transpeptidase activity is localized in the soluble cytoplasmic fraction, while 20–23% of the enzyme is found on the outer surface of the plasmalemma.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1984.tb05905.x
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