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Table 1 Kinetic properties of the four M. truncatula GS isoenzymes

From: Novel aspects of glutamine synthetase (GS) regulation revealed by a detailed expression analysis of the entire GS gene family of Medicago truncatulaunder different physiological conditions

 

GS1a

GS1b

GS2a

GS2b

K m Glu (mM)

2.76 ± 0.22

1.56 ± 0.13

4.47 ± 0.30

6.79 ± 0.58

K m ATP mM

2.34 ± 0.18

1.67 ± 0.17

1.73 ± 0.14

4.76 ± 0.61

K 0.5 Hydroxylamine (mM)

0.90 ± 0.09

0.83 ± 0.08

0.97 ± 0.10

2.09 ± 0.27

h Hydroxylamine

1.97 ± 0.20

1.73 ± 0.16

1.73 ± 0.17

1.57 ± 0.14

GSs (μmol min-1 mg-1)

4.78

2.04

4.46

9.58

GSt (μmol min-1 mg-1)

413

296

251

12

Ratio GSt:GSs

87

145

56

1.2

pH optimum

7.0

7.0

7.5

7.5

  1. The affinity of each GS isoenzyme for the substrates was estimated using the synthetase reaction and 10 μg (GS1a; GS2a and GS2b) or 20 μg (GS1b) of purified protein per assay. Values were automatically calculated by Prism5® software (Graphpad software Inc.) by non-linear least squares regression method assuming either a Michaelis-Menten kinetics (hyperbolic) or an allosteric sigmoidal kinetics. K m – Michaelis-Menten constant; K 0.5 – Half-saturation constant; h – hill coefficient.
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BMC Plant Biology

ISSN: 1471-2229

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