Novel Amino Acid Changes Increase Phosphoenolpyruvate Carboxylase Output in planta.

Three amino acid substitutions in Arabidopsis PHOSPHOENOLPYRUVATE CARBOXYLASE 1 (AtPPC1) are linked to increased aluminum resistance, associated with upwards of threefold higher Al-chelating malate release from roots.

• Why it matters: Aluminum resistance in plants is constrained by how effectively roots release Al-chelating malate, and PHOSPHOENOLPYRUVATE CARBOXYLASE 1 is a key anaplerotic carbon fixation enzyme.
• What they did: The study expressed mutant AtPPC1 variants in an Arabidopsis ppc1 loss-of-function mutant, then used enzyme kinetics and protein structure to show each substitution affects malate–active site interplay; analogous changes were introduced into maize ZmPPC1 and ZmPEP7.
• The result: Maize ZmPPC1 and ZmPEP7 variants showed similar or greater improvements in enzyme activity and reduced regulation in vitro, and a ZmPEP7 transgenic increased PPC-dependent output in planta.

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