Optimized nitrate reductase assay predicts the rate of nitrate utilization in the halotolerant microalga Dunaliella viridis |
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Authors: | F Javier L Gordillo Carlos Jiménez Alfonso Corzo F Xavier Niell |
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Institution: | (1) Departamento de Ecología, Facultad of Ciencias, Universidad de Málaga, 29071 Málaga, Spain;(2) Departamento de Ecología, Facultad de Ciencias del Mar, Universidad de Cádiz, Cádiz, Spain |
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Abstract: | An in situ method for measuring nitrate reductase (NR) activity in Dunaliella viridis was optimized in terms of incubation
time, concentration of KNO3, permeabilisers (1-propanol and toluene), pH, salinity, and reducing power (glucose and NADH). NR activity was measured by
following nitrite production and was best assayed with 50 mM KNO3, 1.2 mM NADH, 5% 1-propanol (v/v), at pH 8.5. The estimated half-saturation constant (Ks) for KNO3 was 5 mM. Glucose had no effect as external reducing power source, and NADH concentrations >1.2 mM inhibited NR activity.
Nitrite production was linear up to 20 min; longer incubation did not lead to higher nitrate reduction. The use of the optimized
assay predicted the rate of NO
3
−
removal from the external medium by D. viridis with high degree of precision.
This revised version was published online in September 2006 with corrections to the Cover Date. |
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Keywords: | Nitrate reductase in situ enzymatic activity Dunaliella viridis |
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