Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.
Project description:Pseudoexfoliation syndrome (PEX) is a systemic disorder that manifests as a fluffy, proteinaceous fibrillar material throughout the body. In the eye, such deposits result in glaucoma (PEXG), due to impeding aqueous humor outflow. When a patient presents acute glaucoma, it is necessary to remove some of the aqueous fluid within the eye to relief pain and pressure. This label free proteomics dataset was collected from human donors during cataract surgery. The aqueous humor was collected during essential ophthalmic procedures that allowed paracentesis after obtaining informed consents from human subjects without collecting identifiers, but all disease and medication history were collected. The sample collection included non-glaucomatous controls (CTL-GC), those with pseudoexfoliation syndrome (PEX-GC), and synthesized GC-Globulin pure protein (GC-Pure). Approximately 50-120 ul volume of AH was collected by paracentesis and stored in -80C immediately upon acquisition until analysis. Protein extraction was carried out by homogenization of the tissue in extraction buffer (TEAB, NaCl and SDS). Protein amounts were estimated and normalized to 10 ug across experimental samples. Samples were reduced using TCEP, alkylated with iodoacetamide and digested overnight with trypsin. Untargeted liquid chromatography-mass spectrometry was performed on an Easy nLC 1000 liquid chromatograph coupled to a QExactive mass spectrometer (LC-MS/MS). Data analysis was performed using Proteome Discoverer 3.0 and Graph Pad Prism 10. Each sample was run three separate times.
Raw mass spectrometry data files were analyzed using Proteome Discoverer 3.0. The human proteome was downloaded from UniProt and used as the target database for protein identification. Max missed cleavage site was set to 2 and minimum peptide length to 6. Precursor Mass Tolerance was set to 10ppm and Fragment Mass Tolerance to 0.02 Da. Post-translational modifications for experimental proteins included oxidation, acetylation, and carbamidomethylation. The normalization was set to total peptide amount and confidence to low.