Mitochondrial Dihydrolipoamide Dehydrogenase (mtLPD1): Expression, Purification, Activity, and Redox Regulation.

Mitochondrial dihydrolipoamide dehydrogenase (mtLPD1) is a central enzyme in primary carbon metabolism, since its function is required to drive four multienzymes involved in photorespiration, the tricarboxylic acid (TCA) cycle, and the degradation of branched-chain amino acids. However, in illuminated, photosynthesizing tissue a vast amount of mtLPD1 is necessary for glycine decarboxylase (GDC), the key enzyme of photorespiration. In light of the shared role, the functional characterization of mtLPD1 is necessary to understand how the three pathways might interact under different environmental scenarios. This includes the determination of the biochemical properties and all potential regulatory mechanisms, respectively. With regards to the latter, regulation can occur through multiple levels including effector molecules, cofactor availability, or posttranslational modifications (PTM), which in turn decrease or increase the activity of each enzymatic reaction. Gaining a comprehensive overview on all these aspects would ultimately facilitate the interpretation of the metabolic interplay of the pathways within the whole subcellular network or even function as a proof of concept for genetic engineering approaches. Here, we describe the typical workflow how to clone, express, and purify plant mtLPD1 for biochemical characterization and how to analyze potential redox regulatory mechanisms in vitro and in planta.