Purification, properties, and sequencing of aminoisobutyrate aminotransferases from rat liver

iTRAQ-based quantitative proteomic analysis reveals the toxic mechanism of diclofenac sodium on the kidney of broiler chicken

Diclofenac sodium (DS) is one of the nonsteroidal anti-inflammatory drugs (NSAIDs), which exhibits potent toxicity to birds. To search the molecular mechanism of DS induced nephrotoxicity in broiler chicken, 20 apparently healthy 30-day old broiler chickens were separated randomly into two groups (n = 10): Group A was kept as control while DS was administered at the dose rate of 10 mg/kg body weight in group B through oral gavage. Kidney samples were collected, and the proteins were identified and quantified by iTRAQ. 434 differentially expressed proteins (DEPs) were screened, including 277 up-regulated DEPs and 157 down-regulated DEPs. The functional annotation and classification results indicated that DEPs were significantly enriched in apoptosis and metabolism-related pathways via GO and KEGG analysis. Compared with the control group, the most significant enrichment pathways are "ribosome", "metabolic pathways" and "protein processing in endoplasmic reticulum". Based on the proteomic results and relevant literature, some DEPs that potentially related to the toxicity of DS were screened. The mRNA transcript levels of these DEPs were characterized by qRT-PCR, and the results showed that Slc22a7, Gatm, Glud1, Agxt2 and Gldc were significantly down-regulated, while Gsl, Gpt2 and Asns were significantly up-regulated. We speculate that the toxic mechanism of DS to chicken might be that it induces kidney cell apoptosis, interferes with purine metabolism and inhibits the expression of OAT2. The current study provides a reference for elucidating the nephrotoxic mechanism of diclofenac sodium to broiler chicken from the molecular perspective.

Bioinformatic analysis of a PLP-dependent enzyme superfamily suitable for biocatalytic applications

In this review we analyse structure/sequence-function relationships for the superfamily of PLP-dependent enzymes with special emphasis on class III transaminases. Amine transaminases are highly important for applications in biocatalysis in the synthesis of chiral amines. In addition, other enzyme activities such as racemases or decarboxylases are also discussed. The substrate scope and the ability to accept chemically different types of substrates are shown to be reflected in conserved patterns of amino acids around the active site. These findings are condensed in a sequence-function matrix, which facilitates annotation and identification of biocatalytically relevant enzymes and protein engineering thereof.

Molecular identification of hydroxylysine kinase and of ammoniophospholyases acting on 5-phosphohydroxy-L-lysine and phosphoethanolamine

The purpose of the present work was to identify the catalytic activity of AGXT2L1 and AGXT2L2, two closely related, putative pyridoxal-phosphate-dependent enzymes encoded by vertebrate genomes. The existence of bacterial homologues (40-50% identity with AGXT2L1 and AGXT2L2) forming bi- or tri-functional proteins with a putative kinase belonging to the family of aminoglycoside phosphotransferases suggested that AGXT2L1 and AGXT2L2 acted on phosphorylated and aminated compounds. Vertebrate genomes were found to encode a homologue (AGPHD1) of these putative bacterial kinases, which was therefore likely to phosphorylate an amino compound bearing a hydroxyl group. These and other considerations led us to hypothesize that AGPHD1 corresponded to 5-hydroxy-L-lysine kinase and that AGXT2L1 and AGXT2L2 catalyzed the pyridoxal-phosphate-dependent breakdown of phosphoethanolamine and 5-phosphohydroxy-L-lysine. The three recombinant human proteins were produced and purified to homogeneity. AGPHD1 was indeed found to catalyze the GTP-dependent phosphorylation of 5-hydroxy-L-lysine. The phosphorylation product made by this enzyme was metabolized by AGXT2L2, which converted it to ammonia, inorganic phosphate, and 2-aminoadipate semialdehyde. AGXT2L1 catalyzed a similar reaction on phosphoethanolamine, converting it to ammonia, inorganic phosphate, and acetaldehyde. AGPHD1 and AGXT2L2 are likely to be the mutated enzymes in 5-hydroxylysinuria and 5-phosphohydroxylysinuria, respectively. The high level of expression of AGXT2L1 in human brain, as well as data in the literature linking AGXT2L1 to schizophrenia and bipolar disorders, suggest that these diseases may involve a perturbation of brain phosphoethanolamine metabolism. AGXT2L1 and AGXT2L2, the first ammoniophospholyases to be identified, belong to a family of aminotransferases acting on ω-amines.