Characterization of an oxaloacetate decarboxylase that belongs to the malic enzyme family

Sender, Pablo D.; Martín, María Julia; Peirú, Salvador; Magni, Christian

doi:10.1016/j.febslet.2004.06.038

Cited by 41 publications

(49 citation statements)

References 27 publications

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“…Oxaloacetate decarboxylase of L. lactis encoded by the mae gene belongs to the second group, and no OAD genes are carried on the chromosome. The mae gene product of L. lactis is the only soluble oxaloacetate decarboxylase that has been characterized in detail (25). The deletion mutant was created by a frameshift deletion of 14 bp between positions 584 and 598 in the gene (1).…”

Section: Discussionmentioning

confidence: 99%

“…Following uptake by the secondary citrate transporter CitP, citrate lyase (CL) converts citrate to acetate and oxaloacetate. Acetate is not further metabolized and leaves the cells, while oxaloacetate is decarboxylated to pyruvate by a soluble oxaloacetate decarboxylase encoded by the mae gene and termed CitM (25). In a recent study it was demonstrated that in the lactic acid bacterium Lactococcus lactis IL1403(pFL3), part of the pyruvate formed from citrate was converted into acetoin and part was converted into acetate in parallel pathways (23).…”

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confidence: 99%

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Mechanism of Citrate Metabolism by an Oxaloacetate Decarboxylase-Deficient Mutant of Lactococcus lactis IL1403

Pudlik

Lolkema

2011

J Bacteriol

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Citrate metabolism plays an important role in many food fermentation processes involving lactic acid bacteria (LAB) (11). Citrate is the precursor of carbon dioxide and the flavor compounds diacetyl and acetoin that contribute to the organoleptic properties of fermented foods. The flavor compounds are formed from the central metabolite pyruvate in the cytoplasm. Citrate metabolism feeds directly into the pyruvate pool (Fig. 1). Following uptake by the secondary citrate transporter CitP, citrate lyase (CL) converts citrate to acetate and oxaloacetate. Acetate is not further metabolized and leaves the cells, while oxaloacetate is decarboxylated to pyruvate by a soluble oxaloacetate decarboxylase encoded by the mae gene and termed CitM (25). In a recent study it was demonstrated that in the lactic acid bacterium Lactococcus lactis IL1403(pFL3), part of the pyruvate formed from citrate was converted into acetoin and part was converted into acetate in parallel pathways (23). In resting cells, the distribution over the two end products strongly depended on the conditions. A high turnover rate through the pathway favored the formation of acetoin over acetate.The citrate transporter CitP plays a pivotal role in the kinetics of the pathway. Under physiological conditions, when citrate is cometabolized with a carbohydrate, CitP operates in the fast citrate/L-lactate exchange mode; citrate is taken up and at the same time that L-lactate, the product of glycolysis, is excreted (precursor/product exchange) (2,17,19,23). In the absence of L-lactate, CitP operates in the much slower unidirectional H ϩ -symport mode (19), which makes uptake the rate-determining step for the flux through the pathway (23). It was shown that, in addition to L-lactate, CitP has an affinity for intermediates/products of the pathway, which results in the typical biphasic consumption of citrate in the absence of L-lactate. During the first phase, citrate is taken up slowly in symport with an H ϩ , but as intermediates/products accumulate in the cytoplasm, the transporter switches to the fast exchange mode, in which citrate is taken up in exchange with pyruvate, ␣-acetolactate, and/or acetate, resulting in much higher consumption rates in the second phase. Therefore, the kinetics and product profile of citrate metabolism are determined largely by the availability of exchangeable substrates for the transporter CitP.The physiological function of citrate metabolism in LAB is in metabolic energy generation and acid stress resistance (8,18,20,28). The citrate metabolic pathway generates proton motive force (PMF) (3,19,20) by an indirect proton pumping mechanism, by which the two components of the PMF, membrane potential (⌬) and pH gradient (⌬pH), are generated in separate steps (13,14). The exchange of divalent citrate and monovalent lactate catalyzed by CitP generates membrane po-

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Mechanism of Citrate Metabolism by an Oxaloacetate Decarboxylase-Deficient Mutant of Lactococcus lactis IL1403

Pudlik

Lolkema

2011

J Bacteriol

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“…Therefore, like for malolactic fermentation, the proton motive force-generating system is built around a precursor/product exchanger (CitP) and a decarboxylase (CitM). The latter was recently shown to be a member of the malic enzyme family, to which malolactic enzyme (MleS) and the oxidative malate decarboxylase (MalS) also belong (129). The oxaloacetate decarboxylases are closely related to the MalS type of malic enzymes, which decarboxylate malate to pyruvate.…”

Section: Physiological Functionmentioning

confidence: 99%

“…NAD ϩ /NADH was shown to be nonessential to the oxaloacetate decarboxylation activity. Nevertheless, the cofactor binding site appears to be conserved in the CitM proteins, and the ability to bind NAD ϩ and NADH was demonstrated by inhibition of enzyme activity in their presence (129).…”

Section: Physiological Functionmentioning

confidence: 99%

The 2-Hydroxycarboxylate Transporter Family: Physiology, Structure, and Mechanism

Sobczak

Lolkema

2005

Microbiol Mol Biol Rev

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SUMMARY The 2-hydroxycarboxylate transporter family is a family of secondary transporters found exclusively in the bacterial kingdom. They function in the metabolism of the di- and tricarboxylates malate and citrate, mostly in fermentative pathways involving decarboxylation of malate or oxaloacetate. These pathways are found in the class Bacillales of the low-CG gram-positive bacteria and in the gamma subdivision of the Proteobacteria. The pathways have evolved into a remarkable diversity in terms of the combinations of enzymes and transporters that built the pathways and of energy conservation mechanisms. The transporter family includes H+ and Na+ symporters and precursor/product exchangers. The proteins consist of a bundle of 11 transmembrane helices formed from two homologous domains containing five transmembrane segments each, plus one additional segment at the N terminus. The two domains have opposite orientations in the membrane and contain a pore-loop or reentrant loop structure between the fourth and fifth transmembrane segments. The two pore-loops enter the membrane from opposite sides and are believed to be part of the translocation site. The binding site is located asymmetrically in the membrane, close to the interface of membrane and cytoplasm. The binding site in the translocation pore is believed to be alternatively exposed to the internal and external media. The proposed structure of the 2HCT transporters is different from any known structure of a membrane protein and represents a new structural class of secondary transporters.

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“…The malic enzyme catalyzes oxaloacetate decarboxylation as the second partial reaction in the conversion of malate to CO 2 plus pyruvate with the reduction of NAD to NADH (41). CitM within the malic enzyme family has evolved to function in a specialized citrate degradation pathway in a small group of Gram-positive bacteria (42). The CitM cannot convert malate to oxaloacetate but it does decarboxylate oxaloacetate at an efficiency of k cat = 20 s −1 and K m = 0.5 mM using the same catalytic residues of the malic enzyme.…”

Section: Pa4872 Catalytic Mechanismmentioning

confidence: 99%

Structure and Function of PA4872 from Pseudomonas aeruginosa, a Novel Class of Oxaloacetate Decarboxylase from the PEP Mutase/Isocitrate Lyase Superfamily^,

et al. 2007

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Pseudomonas aeruginosa PA4872 was identified by sequence analysis as a structurally and functionally novel member of the PEP mutase/isocitrate lyase superfamily and therefore targeted for investigation. Substrate screens ruled out overlap with known catalytic functions of superfamily members. The crystal structure of PA4872 in complex with oxalate (a stable analog of the shared family α-oxyanion carboxylate intermediate/transition state) and Mg 2+ was determined at 1.9 Å resolution. As with other PEP mutase/isocitrate lyase superfamily members, the protein assembles into a dimer of dimers with each subunit adopting an α/β barrel fold and two subunits swapping their barrel's C-terminal α-helices. Mg 2+ and oxalate bind in the same manner as observed with other superfamily members. The active site gating loop, known to play a catalytic role in the PEP mutase and lyase branches of the superfamily, adopts an open conformation. The N ε of His235, an invariant residue in the PA4872 sequence family, is oriented towards a C(2) oxygen of oxalate analogous to the C(3) of a pyruvyl moiety. Deuterium exchange into α-oxocarboxylate-containing compounds was confirmed by 1 H-NMR spectroscopy. Having ruled out known activities, the involvement of a pyruvate enolate intermediate suggested a decarboxylase activity of an α-oxocarboxylate substrate. Enzymatic assays led to the discovery that PA4872 decarboxylates oxaloacetate (k cat = 7500 s −1 and K m = 2.2 mM) and 3-methyloxaloacetate (k cat = 250 s −1 and K m = 0.63 mM). Genome context of the fourteen sequence family members indicates that the enzyme is used by select group of Gramnegative bacteria to maintain cellular concentrations of bicarbonate and pyruvate; however the decarboxylation activity cannot be attributed to a pathway common to the various bacterial species.

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Characterization of an oxaloacetate decarboxylase that belongs to the malic enzyme family

Cited by 41 publications

References 27 publications

Mechanism of Citrate Metabolism by an Oxaloacetate Decarboxylase-Deficient Mutant of Lactococcus lactis IL1403

Mechanism of Citrate Metabolism by an Oxaloacetate Decarboxylase-Deficient Mutant of Lactococcus lactis IL1403

The 2-Hydroxycarboxylate Transporter Family: Physiology, Structure, and Mechanism

Structure and Function of PA4872 from Pseudomonas aeruginosa, a Novel Class of Oxaloacetate Decarboxylase from the PEP Mutase/Isocitrate Lyase Superfamily^,

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Characterization of an oxaloacetate decarboxylase that belongs to the malic enzyme family

Cited by 41 publications

References 27 publications

Mechanism of Citrate Metabolism by an Oxaloacetate Decarboxylase-Deficient Mutant of Lactococcus lactis IL1403

Mechanism of Citrate Metabolism by an Oxaloacetate Decarboxylase-Deficient Mutant of Lactococcus lactis IL1403

The 2-Hydroxycarboxylate Transporter Family: Physiology, Structure, and Mechanism

Structure and Function of PA4872 from Pseudomonas aeruginosa, a Novel Class of Oxaloacetate Decarboxylase from the PEP Mutase/Isocitrate Lyase Superfamily,

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Structure and Function of PA4872 from Pseudomonas aeruginosa, a Novel Class of Oxaloacetate Decarboxylase from the PEP Mutase/Isocitrate Lyase Superfamily^,