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. Author manuscript; available in PMC: 2017 May 24.
Published in final edited form as: Biochemistry. 2016 May 12;55(20):2864–2874. doi: 10.1021/acs.biochem.6b00343

Table 2.

Steady-state kinetic parameters for ATAS mutants

Mutant kcat (s−1) KM (μM) kcat/KM (M−1s−1)
wild-type 0.027 ± 0.003 0.099 ± 0.05 2.7 × 105
S303A 0.045 ± 0.002 0.12 ± 0.02 3.7 × 105
S303H 0.0013 ± 0.0002 0.061 ± 0.02 2.1 × 104
S303D 0.00041 ± 0.00004 0.36 ± 0.09 1.1 × 103
N299A 0.012 ± 0.0004 0.41 ± 0.06 2.9 × 104
N299Va --- --- ---
N299Lb --- --- ---
N299A/S303A 0.0058 ± 0.0003 0.41 ± 0.09 1.4 × 104
Q151H 0.00063 ± 0.0002 0.042 ± 0.01 1.5 × 104
Q151E 0.0015 ± 0.0006 0.10 ± 0.04 1.5 × 104
a

N299V ATAS is soluble and exists as a dimer in solution, but we were unable to measure the generation of any terpenoid products.

b

Although N299L ATAS suffers from compromised thermostability, and its tendency for aggregation hindered the measurement of steady-state kinetic parameters, this mutant generated sufficient sesquiterpene products for analysis as outlined in Figure 3.