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Table 2 Kinetic parameters of AcCS, AcGDH and AcSPAT

From: Molecular and biochemical characterization of key enzymes in the cysteine and serine metabolic pathways of Acanthamoeba castellanii

Recombinant proteins Substrate/cofactor Km (mM) Specific activity (mmol/min per mg of protein) kcat (-s)
AcCS O-acetylserine 0.39 ± 0.02 63.92 ± 6.33  
Na2S 1.44 ± 0.08 0.28 ± 0.01 2.36 × 104 ± 978
AcGDH Hydroxypyruvate 17.93 ± 1.71 26.50 ± 0.85  
NADPH 1.01 ± 0.06 2.05 ± 0.04 9.5 × 103 ± 297
Glycerate 213.80 ± 19.77 20.48 ± 0.65  
NADP+ 19.90 ± 0.74 20.85 ± 0.17 1.38 × 104 ± 273
AcSPAT Pyruvate 5.26 ± 0.40 6.98 ± 0.18  
Serine 0.72 ± 0.03 13.17 ± 0.19 6.66 × 103 ± 122
  1. The enzyme assays were performed by varying one substrate concentration in the presence of a saturating concentration of the other substrate (see the experimental section). The kcat values reported are the means calculated from the Vmax values obtained for both substrates for each enzyme (the kcat for AcCS was obtained using OAS and Na2S; the kcat for the forward reaction of AcGDH was obtained using hydroxypyruvate and NADPH, whereas that for the reverse reaction was obtained using glycerate and NADP+; the kcat for AcSPAT was obtained using pyruvate and serine). Reactions were performed at 37 °C and results represent means ± SD from triple experiments