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Background: Amidotransferases use the amide nitrogen of glutamine in a number of important biosynthetic reactions. They are composed of a glutaminase domain, which catalyzes the hydrolysis of glutamine to glutamate and ammonia, and a synthetase domain, catalyzing amination of the substrate. To gain insight into the mechanism of nitrogen transfer, we examined the structure of the glutaminase domain...
Background: Phosphoglycerate kinase (PGK) is essential in most living cells both for ATP generation in the glycolytic pathway of aerobes and for fermentation in anaerobes. In addition, in many plants the enzyme is involved in carbon fixation. Like other kinases, PGK folds into two distinct domains, which undergo a large hinge-bending motion upon catalysis. The monomeric 45 kDa enzyme catalyzes the...
Background: Arginase is a manganese-dependent enzyme that catalyzes the hydrolysis of L-arginine to L-ornithine and urea. In ureotelic animals arginase is the final enzyme of the urea cycle, but in many species it has a wider role controlling the use of arginine for other metabolic purposes, including the production of creatine, polyamines, proline and nitric oxide. Arginase activity is regulated...
Background: Conversion of 5-aminoimidazole ribonucleotide (AIR) to 4-carboxyaminoimidazole ribonucleotide (CAIR) in Escherichia coli requires two proteins - PurK and PurE. PurE has recently been shown to be a mutase that catalyzes the unusual rearrangement of N 5 -carboxyaminoimidazole ribonucleotide (N 5 -CAIR), the PurK reaction product, to CAIR. PurEs from higher eukaryotes are...
Background: β-Keto acyl carrier protein reductase (BKR) catalyzes the pyridine-nucleotide-dependent reduction of a 3-oxoacyl form of acyl carrier protein (ACP), the first reductive step in de novo fatty acid biosynthesis and a reaction often performed in polyketide biosynthesis. The Brassica napus BKR enzyme is NADPH-dependent and forms part of a dissociable type II fatty acid synthetase (FAS). Significant...
Background: N-carbamyl-d-amino acid amidohydrolase (DCase) catalyzes the hydrolysis of N-carbamyl-d-amino acids to the corresponding d-amino acids, which are useful intermediates in the preparation of β-lactam antibiotics. To understand the catalytic mechanism of N-carbamyl-d-amino acid hydrolysis, the substrate specificity and thermostability of the enzyme, we have determined the structure of DCase...
Background: β-ketoacyl-acyl carrier protein synthase (KAS) I is vital for the construction of the unsaturated fatty acid carbon skeletons characterizing E. coli membrane lipids. The new carbon-carbon bonds are created by KAS I in a Claisen condensation performed in a three-step enzymatic reaction. KAS I belongs to the thiolase fold enzymes, of which structures are known for five other enzymes.Results:...
Background: Sulfatases constitute a family of enzymes with a highly conserved active site region including a Cα-formylglycine that is posttranslationally generated by the oxidation of a conserved cysteine or serine residue. The crystal structures of two human arylsulfatases, ASA and ASB, along with ASA mutants and their complexes led to different proposals for the catalytic mechanism in the hydrolysis...
The crystal structures of Salmonella typhimurium 4-amino-5-hydroxymethyl-2-methylpyrimidine phosphate kinase (HMPP kinase) and its complex with substrate HMP have been determined. HMPP kinase catalyzes two separate ATP-dependent phosphorylation reactions and is an essential enzyme in the thiamin biosynthetic pathway. HMPP kinase is a homodimer with one active site per monomer and is structurally homologous...
Kumamolysin is a thermostable endopeptidase from Bacillus novosp. MN-32, exhibiting maximal proteolytic activity around pH 3. It belongs to the newly identified family of serine-carboxyl proteinases, which also includes CLN2, a human lysosomal homolog recently implicated in a fatal neurodegenerative disease. Kumamolysin and its complexes with two aldehyde inhibitors were crystallized, and their three-dimensional...
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