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Table 2. Michaelis-Menten parameters for Drosophila melaonogaster soluble guanylyl cyclase subunits transiently transfected in COS-7 cells.
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V max (pmoles cGMP/min/mg protein) |
K m (mM) |
|
Mg a |
Mn b |
Mn/Mg |
Mg c |
Mn d |
Mg/Mn |
Gyc-88EL |
1.32 ± 0.33 |
2.26 ± 0.16 |
1.71 |
1.73 ± 1.30 |
0.032 ± 0.011 |
54.1 |
Gyc-88EL + Gyc-89Da |
1.92 ± 0.65 |
90.1 ± 2.34 |
46.9 |
2.06 ± 1.95 |
0.149 ± 0.014 |
13.8 |
Gyc-88EL + Gyc-89Db |
4.83 ± 0.33 |
8.72 ± 0.82 |
1.81 |
0.89 ± 0.17 |
0.0094 ± 0.0048 |
94.7 |
Gyc a -99B + Gyc b -100B |
2.11 ± 0.10 |
204 ± 10.6 |
96.7 |
0.37 ± 0.06 |
0.031 ± 0.008 |
11.9 |
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|
COS-7 cells were transiently transfected with the subunits as shown and the cell extracts assayed for guanylyl cyclase activity in the presence of different concentrations of GTP. Estimated values for Vmax and Km for each subunit or combination of subunits were calculated from the data shown in Figure 2. The data were then analyzed by two-way ANOVA followed by Bonferroni post-tests: a – the value of Vmax in Mg for Gyc-88EL/89Db was significantly (p<0.001) higher than for each of the other subunits and no other subunit comparisons were significantly different; b – the values of Vmax in Mn for each subunit combination were significantly (p<0.001) different from each of the other subunit combinations with the exception of Gyc-88EL v's Gyc-88EL/89Db which were not significantly different from each other; c – there was no significant difference between the values for the Km in Mg for each subunit combination; d – the value of Km in Mn of Gyc-88EL/89Da was significantly (p<0.001) higher than each of the other subunit combinations and no other subunit comparisons were significantly different.
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