Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Structure of the PLP-Form of the Human Kynurenine Aminotransferase II in a Novel Spacegroup at 1.83 A Resolution.

ABSTRACT: Kynurenine aminotransferase II (KAT-II) is a 47 kDa pyridoxal phosphate (PLP)-dependent enzyme, active as a homodimer, which catalyses the transamination of the amino acids kynurenine (KYN) and 3-hydroxykynurenine (3-HK) in the tryptophan pathway, and is responsible for producing metabolites that lead to kynurenic acid (KYNA), which is implicated in several neurological diseases such as schizophrenia. In order to fully describe the role of KAT-II in the pathobiology of schizophrenia and other brain disorders, the crystal structure of full-length PLP-form hKAT-II was determined at 1.83 Å resolution, the highest available. The electron density of the active site reveals an aldimine linkage between PLP and Lys263, as well as the active site residues, which characterize the fold-type I PLP-dependent enzymes.

SUBMITTER: Nematollahi A

PROVIDER: S-EPMC4848902 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Structure of the PLP-Form of the Human Kynurenine Aminotransferase II in a Novel Spacegroup at 1.83 Å Resolution.

Nematollahi Alireza A Sun Guanchen G Harrop Stephen J SJ Hanrahan Jane R JR Church W Bret WB

International journal of molecular sciences 20160325 4

Kynurenine aminotransferase II (KAT-II) is a 47 kDa pyridoxal phosphate (PLP)-dependent enzyme, active as a homodimer, which catalyses the transamination of the amino acids kynurenine (KYN) and 3-hydroxykynurenine (3-HK) in the tryptophan pathway, and is responsible for producing metabolites that lead to kynurenic acid (KYNA), which is implicated in several neurological diseases such as schizophrenia. In order to fully describe the role of KAT-II in the pathobiology of schizophrenia and other br ...[more]

PMID: 27023527

Similar Datasets

Substrate specificity and structure of human aminoadipate aminotransferase/kynurenine aminotransferase II.

Project description:KAT (kynurenine aminotransferase) II is a primary enzyme in the brain for catalysing the transamination of kynurenine to KYNA (kynurenic acid). KYNA is the only known endogenous antagonist of the N-methyl-D-aspartate receptor. The enzyme also catalyses the transamination of aminoadipate to alpha-oxoadipate; therefore it was initially named AADAT (aminoadipate aminotransferase). As an endotoxin, aminoadipate influences various elements of glutamatergic neurotransmission and kills primary astrocytes in the brain. A number of studies dealing with the biochemical and functional characteristics of this enzyme exist in the literature, but a systematic assessment of KAT II addressing its substrate profile and kinetic properties has not been performed. The present study examines the biochemical and structural characterization of a human KAT II/AADAT. Substrate screening of human KAT II revealed that the enzyme has a very broad substrate specificity, is capable of catalysing the transamination of 16 out of 24 tested amino acids and could utilize all 16 tested alpha-oxo acids as amino-group acceptors. Kinetic analysis of human KAT II demonstrated its catalytic efficiency for individual amino-group donors and acceptors, providing information as to its preferred substrate affinity. Structural analysis of the human KAT II complex with alpha-oxoglutaric acid revealed a conformational change of an N-terminal fraction, residues 15-33, that is able to adapt to different substrate sizes, which provides a structural basis for its broad substrate specificity.

| S-EPMC2559858 | biostudies-literature

High resolution crystal structures of human kynurenine aminotransferase-I bound to PLP cofactor, and in complex with aminooxyacetate.

Project description:In this study, we report two high-resolution structures of the pyridoxal 5' phosphate (PLP)-dependent enzyme kynurenine aminotransferase-I (KAT-I). One is the native structure with the cofactor in the PLP form bound to Lys247 with the highest resolution yet available for KAT-I at 1.28 Å resolution, and the other with the general PLP-dependent aminotransferase inhibitor, aminooxyacetate (AOAA) covalently bound to the cofactor at 1.54 Å. Only small conformational differences are observed in the vicinity of the aldimine (oxime) linkage with which the PLP forms the Schiff base with Lys247 in the 1.28 Å resolution native structure, in comparison to other native PLP-bound structures. We also report the inhibition of KAT-1 by AOAA and aminooxy-phenylpropionic acid (AOPP), with IC50s of 13.1 and 5.7 μM, respectively. The crystal structure of the enzyme in complex with the inhibitor AOAA revealed that the cofactor is the PLP form with the external aldimine linkage. The location of this oxime with the PLP, which forms in place of the native internal aldimine linkage of PLP of the native KAT-I, is away from the position of the native internal aldimine, with the free Lys247 substantially retaining the orientation of the native structure. Tyr101, at the active site, was observed in two conformations in both structures.

| S-EPMC5368072 | biostudies-literature

Improvement of kynurenine aminotransferase-II inhibitors guided by mimicking sulfate esters.

Project description:The mammalian kynurenine aminotransferase (KAT) enzymes are a family of related isoforms that are pyridoxal 5'-phosphate-dependent, responsible for the irreversible transamination of kynurenine to kynurenic acid. Kynurenic acid is implicated in human diseases such as schizophrenia where it is found in elevated levels and consequently KAT-II, as the isoform predominantly responsible for kynurenic acid production in the brain, has been targeted for the development of specific inhibitors. One class of compounds that have also shown inhibitory activity towards the KAT enzymes are estrogens and their sulfate esters. Estradiol disulfate in particular is very strongly inhibitory and it appears that the 17-sulfate makes a significant contribution to its potency. The work here demonstrates that the effect of this moiety can be mirrored in existing KAT-II inhibitors, from the development of two novel inhibitors, JN-01 and JN-02. Both inhibitors were based on NS-1502 (IC50: 315 μM), but the deliberate placement of a sulfonamide group significantly improved the potency of JN-01 (IC50: 73.8 μM) and JN-02 (IC50: 112.8 μM) in comparison to the parent compound. This 3-4 fold increase in potency shows the potential of these moieties to be accommodated in the KAT-II active site and the effect they can have on improving inhibitors, and the environments in the KAT-II have been suitably modelled using docking calculations.

| S-EPMC5915280 | biostudies-literature

Crystal structure-based selective targeting of the pyridoxal 5'-phosphate dependent enzyme kynurenine aminotransferase II for cognitive enhancement.

Project description:Fluctuations in the brain levels of the neuromodulator kynurenic acid may control cognitive processes and play a causative role in several catastrophic brain diseases. Elimination of the pyridoxal 5'-phosphate dependent enzyme kynurenine aminotransferase II reduces cerebral kynurenic acid synthesis and has procognitive effects. The present description of the crystal structure of human kynurenine aminotransferase II in complex with its potent and specific primary amine-bearing fluoroquinolone inhibitor (S)-(-)-9-(4-aminopiperazin-1-yl)-8-fluoro-3-methyl-6-oxo-2,3-dihydro-6H-1-oxa-3a-azaphenalene-5-carboxylic acid (BFF-122) should facilitate the structure-based development of cognition-enhancing drugs. From a medicinal chemistry perspective our results demonstrate that the issue of inhibitor specificity for highly conserved PLP-dependent enzymes could be successfully addressed.

| S-EPMC3929320 | biostudies-literature

Heterocyclic Cathinones as Inhibitors of Kynurenine Aminotransferase II-Design, Synthesis, and Evaluation.

Project description:Kynurenic acid is a neuroprotective metabolite of tryptophan formed by kynurenine aminotransferase (KAT) catalyzed transformation of kynurenine. However, its high brain levels are associated with cognitive deficit and with the pathophysiology of schizophrenia. Although several classes of KAT inhibitors have been published, the search for new inhibitor chemotypes is crucial for the process of finding suitable clinical candidates. Therefore, we used pharmacophore modeling and molecular docking, which predicted derivatives of heterocyclic amino ketones as new potential irreversible inhibitors of kynurenine aminotransferase II. Thiazole and triazole-based amino ketones were synthesized within a SAR study and their inhibitory activities were evaluated in vitro. The observed activities confirmed our computational model and, moreover, the best compounds showed sub-micromolar inhibitory activity with 2-alaninoyl-5-(4-fluorophenyl)thiazole having IC50 = 0.097 µM.

| S-EPMC8708382 | biostudies-literature

Inhibition of human kynurenine aminotransferase isozymes by estrogen and its derivatives.

Project description:The kynurenine aminotransferase (KAT) enzymes are pyridoxal 5'-phosphate-dependent homodimers that catalyse the irreversible transamination of kynurenine into kynurenic acid (KYNA) in the tryptophan metabolic pathway. Kynurenic acid is implicated in cognitive diseases such as schizophrenia, and several inhibitors have been reported that selectively target KAT-II as it is primarily responsible for kynurenic acid production in the human brain. Not only is schizophrenia a sexually dimorphic condition, but women that have schizophrenia have reduced estrogen levels in their serum. Estrogens are also known to interact in the kynurenine pathway therefore exploring these interactions can yield a better understanding of the condition and improve approaches in ameliorating its effects. Enzyme inhibitory assays and binding studies showed that estradiol disulfate is a strong inhibitor of KAT-I and KAT-II (IC50: 291.5??M and 26.3??M, respectively), with estradiol, estradiol 3-sulfate and estrone sulfate being much weaker (IC50?>?2?mM). Therefore it is possible that estrogen levels can dictate the balance of kynurenic acid in the brain. Inhibition assay results and modelling suggests that the 17-sulfate moiety in estradiol disulfate is very important in improving its potency as an inhibitor, increasing the inhibition by approximately 10-100 fold compared to estradiol.

| S-EPMC5730616 | biostudies-literature

Kynurenine Aminotransferase Isozyme Inhibitors: A Review.

Project description:Kynurenine aminotransferase isozymes (KATs 1-4) are members of the pyridoxal-5'-phosphate (PLP)-dependent enzyme family, which catalyse the permanent conversion of l-kynurenine (l-KYN) to kynurenic acid (KYNA), a known neuroactive agent. As KATs are found in the mammalian brain and have key roles in the kynurenine pathway, involved in different categories of central nervous system (CNS) diseases, the KATs are prominent targets in the quest to treat neurodegenerative and cognitive impairment disorders. Recent studies suggest that inhibiting these enzymes would produce effects beneficial to patients with these conditions, as abnormally high levels of KYNA are observed. KAT-1 and KAT-3 share the highest sequence similarity of the isozymes in this family, and their active site pockets are also similar. Importantly, KAT-2 has the major role of kynurenic acid production (70%) in the human brain, and it is considered therefore that suitable inhibition of this isozyme would be most effective in managing major aspects of CNS diseases. Human KAT-2 inhibitors have been developed, but the most potent of them, chosen for further investigations, did not proceed in clinical studies due to the cross toxicity caused by their irreversible interaction with PLP, the required cofactor of the KAT isozymes, and any other PLP-dependent enzymes. As a consequence of the possibility of extensive undesirable adverse effects, it is also important to pursue KAT inhibitors that reversibly inhibit KATs and to include a strategy that seeks compounds likely to achieve substantial interaction with regions of the active site other than the PLP. The main purpose of this treatise is to review the recent developments with the inhibitors of KAT isozymes. This treatise also includes analyses of their crystallographic structures in complex with this enzyme family, which provides further insight for researchers in this and related studies.

| S-EPMC4926479 | biostudies-literature

Discovery of Brain-Penetrant, Irreversible Kynurenine Aminotransferase II Inhibitors for Schizophrenia.

Project description:Kynurenine aminotransferase (KAT) II has been identified as a potential new target for the treatment of cognitive impairment associated with schizophrenia and other psychiatric disorders. Following a high-throughput screen, cyclic hydroxamic acid PF-04859989 was identified as a potent and selective inhibitor of human and rat KAT II. An X-ray crystal structure and (13)C NMR studies of PF-04859989 bound to KAT II have demonstrated that this compound forms a covalent adduct with the enzyme cofactor, pyridoxal phosphate (PLP), in the active site. In vivo pharmacokinetic and efficacy studies in rat show that PF-04859989 is a brain-penetrant, irreversible inhibitor and is capable of reducing brain kynurenic acid by 50% at a dose of 10 mg/kg (sc). Preliminary structure-activity relationship investigations have been completed and have identified the positions on this scaffold best suited to modification for further optimization of this novel series of KAT II inhibitors.

| S-EPMC4025856 | biostudies-other

Structural insight into the inhibition of human kynurenine aminotransferase I/glutamine transaminase K.

Project description:Human kynurenine aminotransferase I (hKAT I) catalyzes the formation of kynurenic acid, a neuroactive compound. Here, we report three high-resolution crystal structures (1.50-1.55 A) of hKAT I that are in complex with glycerol and each of two inhibitors of hKAT I: indole-3-acetic acid (IAC) and Tris. Because Tris is able to occupy the substrate binding position, we speculate that this may be the basis for hKAT I inhibition. Furthermore, the hKAT/IAC complex structure reveals that the binding moieties of the inhibitor are its indole ring and a carboxyl group. Six chemicals with both binding moieties were tested for their ability to inhibit hKAT I activity; 3-indolepropionic acid and DL-indole-3-lactic acid demonstrated the highest level of inhibition, and as they cannot be considered as substrates of the enzyme, these two inhibitors are promising candidates for future study. Perhaps even more significantly, we report the discovery of two different ligands located simultaneously in the hKAT I active center for the first time.

| S-EPMC2844090 | biostudies-literature

Characteristic features of kynurenine aminotransferase allosterically regulated by (alpha)-ketoglutarate in cooperation with kynurenine.

Project description:Kynurenine aminotransferase from Pyrococcus horikoshii OT3 (PhKAT), which is a homodimeric protein, catalyzes the conversion of kynurenine (KYN) to kynurenic acid (KYNA). We analyzed the transaminase reaction mechanisms of this protein with pyridoxal-5'-phosphate (PLP), KYN and ?-ketoglutaric acid (2OG) or oxaloacetic acid (OXA). 2OG significantly inhibited KAT activities in kinetic analyses, suggesting that a KYNA biosynthesis is allosterically regulated by 2OG. Its inhibitions evidently were unlocked by KYN. 2OG and KYN functioned as an inhibitor and activator in response to changes in the concentrations of KYN and 2OG, respectively. The affinities of one subunit for PLP or 2OG were different from that of the other subunit, as confirmed by spectrophotometry and isothermal titration calorimetry, suggesting that the difference of affinities between subunits might play a role in regulations of the KAT reaction. Moreover, we identified two active and allosteric sites in the crystal structure of PhKAT-2OG complexes. The crystal structure of PhKAT in complex with four 2OGs demonstrates that two 2OGs in allosteric sites are effector molecules which inhibit the KYNA productions. Thus, the combined data lead to the conclusion that PhKAT probably is regulated by allosteric control machineries, with 2OG as the allosteric inhibitor.

| S-EPMC3391261 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data