title: Escherichia coli D-malate dehydrogenase, a generalist enzyme active in the leucine biosynthesis pathway.
abstract: The enzymes of the β-decarboxylating dehydrogenase superfamily catalyze the oxidative decarboxylation of D-malate-based substrates with various specificities. Here, we show that, in addition to its natural function affording bacterial growth on D-malate as a carbon source, the D-malate dehydrogenase of Escherichia coli (EcDmlA) naturally expressed from its chromosomal gene is capable of complementing leucine auxotrophy in a leuB(-) strain lacking the paralogous isopropylmalate dehydrogenase enzyme. To our knowledge, this is the first example of an enzyme that contributes with a physiologically relevant level of activity to two distinct pathways of the core metabolism while expressed from its chromosomal locus. EcDmlA features relatively high catalytic activity on at least three different substrates (L(+)-tartrate, D-malate, and 3-isopropylmalate). Because of these properties both in vivo and in vitro, EcDmlA may be defined as a generalist enzyme. Phylogenetic analysis highlights an ancient origin of DmlA, indicating that the enzyme has maintained its generalist character throughout evolution. We discuss the implication of these findings for protein evolution.
authors.affiliation: From the Laboratoire de Biochimie, Biophysique et Génétique des Microorganismes (BBGM), Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium and.
authors.forename: Anastassia A
authors.initials: AA
authors.lastname: Vorobieva
authors.affiliation: the Department of Fisheries, University of Dhaka, Dhaka 1000, Bangladesh.
authors.forename: Mohammad Shahneawz
authors.initials: MS
authors.lastname: Khan
authors.affiliation: From the Laboratoire de Biochimie, Biophysique et Génétique des Microorganismes (BBGM), Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium and patrice.soumillion@uclouvain.be.
authors.forename: Patrice
authors.initials: P
authors.lastname: Soumillion
mesh_terms: D002384:Catalysis; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D005470:Fluorometry; D007930:Leucine / Q000096:biosynthesis*; D008291:Malate Dehydrogenase / Q000378:metabolism*; D010641:Phenotype; D010802:Phylogeny; D011401:Promoter Regions, Genetic
chemical_list: D029968:Escherichia coli Proteins; D008291:Malate Dehydrogenase; D007930:Leucine
keywords: Dehydrogenase; Enzyme Catalysis; Enzyme Promiscuity; Metabolism; Multifunctional Enzyme; Protein Evolution