Unusual composition of the mitochondrial pyruvate dehydrogenase complex from the widespread marine protist group diplonemids

ABSTRACT: In eukaryotes, pyruvate, a key metabolite produced by glycolysis, is converted by a mitochondrial pyruvate dehydrogenase complex (PDH) to acetyl-coenzyme A, which is fed into the tricarboxylic acid cycle. Two additional enzyme complexes catalyze similar oxidative decarboxylation reactions albeit using different substrates, the branched-chain ketoacid dehydrogenase (BCKDH) and the 2-oxoglutarate dehydrogenase (OGDH). In diplonemids, one of the most abundant and diverse groups of oceanic protists, comparative transcriptome analyses indicated that their PDH complex is compositionally unique, with the conventional E1 subunit replaced by an aceE protein of prokaryotic origin. Here we demonstrate in the model diplonemid Paradiplonema papillatum that the pyruvate dehydrogenase activity is comparable to that in other euglenozoan protists. By protein mass spectrometry we revealed that the aceE protein is twice as abundant as the E1 subunits of OGDH and enriched in the mitochondrion to the same level as the BCKDH E1 subunits, corroborating the functional relevance of the proposed aceE subunit of the PDH complex. Importantly, the acquisition of the archaeal aceE by the diplonemid ancestor led not only to the complete loss of the eukaryotic-type E1 of the PDH complex, but also its dedicated E2 and E3 subunits, still present in other euglenozoans. Hence, to reconstitute the diplonemid PDH, the aceE protein needs to partner with E2 and E3 subunits of BCKDH and/or OGDH. The diplonemid example illustrates that the acquisition and successful integration of a foreign E1p can profoundly reorganize the entire PDH complex.

INSTRUMENT(S): LTQ Orbitrap Elite

ORGANISM(S): Diplonema Papillatum

SUBMITTER: Maksym Danchenko  

LAB HEAD: Peter Baráth

PROVIDER: PXD035104 | Pride | 2023-07-28

REPOSITORIES: Pride