Association of the malate dehydrogenase‑citrate synthase metabolon is modulated by intermediates of the Krebs tricarboxylic acid cycle

Authors

Joy Omini, University of Nebraska - Lincoln
Izabela Wojciechowska, Max-Planck-Institute of Molecular Plant Physiology
Aleksandra Skirycz, Max-Planck-Institute of Molecular Plant Physiology
Hideaki Moriyama, University of Nebraska at LincolnFollow
Toshihiro Obata, University of Nebraska-LincolnFollow

Date of this Version

2021

Citation

https://doi.org/10.1038/s41598-021-98314-z

Comments

open access

Abstract

Mitochondrial malate dehydrogenase (MDH)-citrate synthase (CS) multi-enzyme complex is a part of the Krebs tricarboxylic acid (TCA) cycle ‘metabolon’ which is enzyme machinery catalyzing sequential reactions without diffusion of reaction intermediates into a bulk matrix. This complex is assumed to be a dynamic structure involved in the regulation of the cycle by enhancing metabolic flux. Microscale Thermophoresis analysis of the porcine heart MDH-CS complex revealed that substrates of the MDH and CS reactions, NAD+ and acetyl-CoA, enhance complex association while products of the reactions, NADH and citrate, weaken the affinity of the complex. Oxaloacetate enhanced the interaction only when it was present together with acetyl-CoA. Structural modeling using published CS structures suggested that the binding of these substrates can stabilize the closed format of CS which favors the MDH-CS association. Two other TCA cycle intermediates, ATP, and low pH also enhanced the association of the complex. These results suggest that dynamic formation of the MDH-CS multienzyme complex is modulated by metabolic factors responding to respiratory metabolism, and it may function in the feedback regulation of the cycle and adjacent metabolic pathways.