Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.2.13 (aldolase)
 3,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The stereospecificities of 2-keto-4-pentenoate hydratase and 4-hydroxy-2-ketovalerate aldolase were studied in Escherichia coli, Pseudomonas putida, and Acinetobacter sp. Hydration was stereospecific in all three; however, only P. putida and Acinetobacter sp. showed stereospecificity in their aldolase reactions.
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PMID:Stereospecificity in meta-fission catabolic pathways. 634 11

The final two steps in the dmp operon-encoded meta-cleavage pathway for phenol degradation in Pseudomonas sp. strain CF600 involve conversion of 4-hydroxy-2-ketovalerate to pyruvate and acetyl coenzyme A (acetyl-CoA) by the enzymes 4-hydroxy-2-ketovalerate aldolase and aldehyde dehydrogenase (acylating) [acetaldehyde:NAD+ oxidoreductase (CoA acetylating), EC 1.2.1.10]. A procedure for purifying these two enzyme activities to homogeneity is reported here. The two activities were found to copurify through five different chromatography steps and ammonium sulfate fractionation, resulting in a preparation that contained approximately equal proportions of two polypeptides with molecular masses of 35 and 40 kDa. Amino-terminal sequencing revealed that the first six amino acids of each polypeptide were those deduced from the previously determined nucleotide sequences of the corresponding dmp operon-encoded genes. The isolated complex had a native molecular mass of 148 kDa, which is consistent with the presence of two of each polypeptide per complex. In addition to generating acetyl-CoA from acetaldehyde, CoA, and NAD+, the dehydrogenase was shown to acylate propionaldehyde, which would be generated by action of the meta-cleavage pathway enzymes on the substrates 3,4-dimethylcatechol and 4-methylcatechol. 4-Hydroxy-2-ketovalerate aldolase activity was stimulated by the addition of Mn2+ and, surprisingly, NADH to assay mixtures. The possible significance of the close physical association between these two polypeptides in ensuring efficient metabolism of the short-chain aldehyde generated by this pathway is discussed.
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PMID:Purification and properties of the physically associated meta-cleavage pathway enzymes 4-hydroxy-2-ketovalerate aldolase and aldehyde dehydrogenase (acylating) from Pseudomonas sp. strain CF600. 841 88

The final two steps of the meta-cleavage pathway for catechol degradation in Pseudomonas sp. strain CF600 involve the conversion of 4-hydroxy-2-ketovalerate to pyruvate and acetyl coenzyme A by the enzymes 4-hydroxy-2-ketovalerate aldolase and NAD(+)-dependent acylating aldehyde dehydrogenase. Biochemical studies indicate that these two enzymes comprise a bifunctional heterodimer (DmpFG, molecular mass 71 kDa) and suggest that the product of the aldolase reaction is transferred to the dehydrogenase active site via a channeling mechanism. Crystals of the DmpFG complex grow in multiple fan-like clusters of thin plates by the hanging-drop method and are improved by streak-seeding. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 102.0, b = 140.7, c = 191.3 A, and diffract to 2.1 A resolution. The asymmetric unit contains four DmpFG heterodimers. Heavy-atom derivative screening identified three isomorphous derivatives.
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PMID:Crystallization and preliminary X-ray analysis of dmpFG-encoded 4-hydroxy-2-ketovalerate aldolase--aldehyde dehydrogenase (acylating) from Pseudomonas sp. strain CF600. 1126 89

MhpE (4-hydroxy-2-ketovalerate aldolase) and MhpF [acetaldehyde dehydrogenase (acylating)] are responsible for the last two reactions in the 3-(3-hydroxyphenyl)propionate (3-HPP) catabolic pathway in Escherichia coli, which is homologous to the meta-cleavage pathway in Pseudomonas species. Here, we report that the MhpE aldolase is associated with the MhpF dehydrogenase and that MhpF is indispensable for the folding of MhpE. Moreover, our results suggest that the mhpF and mhpE genes are translationally coupled through a reinitiation mechanism. This reinitiation mechanism may function in ensuring that the expression of mhpE occurs only when MhpF is available for the formation of a complex.
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PMID:Coupled expression of MhpE aldolase and MhpF dehydrogenase in Escherichia coli. 1678 65

The bifunctional, microbial enzyme DmpFG is comprised of two subunits: the aldolase, DmpG, and the dehydrogenase, DmpF. DmpFG is of interest due to its ability to channel substrates between the two spatially distinct active sites. While the aldolase is well studied, significantly less is known about the dehydrogenase. Steady-state kinetic measurements of the reverse reaction of DmpF confirmed that the dehydrogenase uses a ping-pong mechanism, with substrate inhibition by acetyl CoA indicating that NAD(+)/NADH and CoA/acetyl CoA bind to the same site in DmpF. The Km of DmpF for exogenous acetaldehyde as a substrate was 23.7 mM, demonstrating the necessity for the channel to deliver acetaldehyde directly from the aldolase to the dehydrogenase active site. A channeling assay on the bifunctional enzyme gave an efficiency of 93% indicating that less than 10% of the toxic acetaldehyde leaks out of the channel into the bulk media, prior to reaching the dehydrogenase active site. The thermodynamic activation parameters of the reactions catalyzed by the aldolase, the dehydrogenase and the DmpFG complex were determined. The Gibb's free energy of activation for the dehydrogenase reaction was lower than that obtained for the full DmpFG reaction, in agreement with the high kcat obtained for the dehydrogenase reaction in isolation. Furthermore, although both the DmpF and DmpG reactions occur with small, favorable entropies of activation, the full DmpFG reaction occurs with a negative entropy of activation. This supports the concept of allosteric structural communication between the two enzymes to coordinate their activities.
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PMID:Mechanism of the dehydrogenase reaction of DmpFG and analysis of inter-subunit channeling efficiency and thermodynamic parameters in the overall reaction. 2374 89

DmpFG is a bifunctional enzyme comprised of an aldolase subunit, DmpG, and a dehydrogenase subunit, DmpF. The aldehyde intermediate produced by the aldolase is channeled directly through a buried molecular channel in the protein structure from the aldolase to the dehydrogenase active site. In this study, we have investigated the binding of a series of progressively larger substrates to the aldolase, DmpG, using molecular dynamics. All substrates investigated are easily accommodated within the active site, binding with free energy values comparable to the physiological substrate 4-hydroxy-2-ketovalerate. Subsequently, umbrella sampling was utilized to obtain free energy surfaces for the aldehyde intermediates (which would be generated from the aldolase reaction on each of these substrates) to move through the channel to the dehydrogenase DmpF. Small substrates were channeled with limited barriers in an energetically feasible process. We show that the barriers preventing bulky intermediates such as benzaldehyde from moving through the wild-type protein can be removed by selective mutation of channel-lining residues, demonstrating the potential for tailoring this enzyme to allow its use for the synthesis of specific chemical products. Furthermore, positions of transient escape routes in this flexible channel were determined.
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PMID:Binding and channeling of alternative substrates in the enzyme DmpFG: a molecular dynamics study. 2473 67