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. 2010 Dec 15;433(Pt 1):65–74. doi: 10.1042/BJ20101361

Figure 6. Influence of L-malate, L-aspartate and assay pH on activity of Class-2 PEPC mutants.

Figure 6

(A and B) PEPC activity was determined at pH 7.0 with subsaturating PEP (0.2 and 1 mM for RcPPC4 wild-type and RcPPC4_R644A mutants respectively) in the presence of increasing concentrations of L-malate and L-aspartate. Shown are the I50(malate) (A) or I50(aspartate) (B) values for several subunit combinations of Class-2 PEPC. The PTPC subunit was either wild-type (wt) AtPPC3 or an inactive mutant (AtPPC3_R644A). The BTPC subunit was either wild-type (wt) (RcPPC4), inactive (RcPPC4_R760A) or active (RcPPC4_P426A, RcPPC4_S425D and RcPPC4_S425A) site-directed mutants. All values represent the means±S.E.M. of at least four separate determinations. (C) PEPC activity was determined with saturating PEP (25 mM) at various pH values using a mixture of 25 mM MES and 25 mM bis-Tris-propane as the assay buffer. (●) AtPPC3_R644A/RcPPC4, (○) AtPPC3_R644A/RcPPC4_S425D and (▼) AtPPC3_R644A/RcPPC4_P426A. All values represent the means of three different experiments and are reproducible to within ±10% S.E.M. of the mean value.