Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.3.4.6 (urease)
 7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nucleotide sequence of the selA gene from Escherichia coli whose product is involved in the conversion of seryl-tRNA(Sec UCA) into selenocysteyl-tRNA(Sec UCA) was determined. selA codes for a polypeptide of a calculated Mr of 50,667; a protein of appropriate size was synthesized in vivo in a T7 promoter/polymerase system. An assay for SELA activity was devised which is based on the seryl-tRNA(Sec UCA)-dependent incorporation of [75Se] selenium into acid-insoluble material. It was used to follow SELA purification from cells that overproduced the protein from a phage T7 promoter plasmid. Purified native SELA protein migrates in gel filtration experiments with a native Mr of about 600,000. SELA contains 1 mol of bound pyridoxal 5-phosphate/mol of 50-kDa subunit. Evidence is presented that the overall conversion of seryl-tRNA(Sec UCA) to selenocysteyl-tRNA(Sec UCA) occurs at the SELA protein. SELA, therefore, has the function of a selenocysteine synthase.
 ...
PMID:Selenocysteine synthase from Escherichia coli. Nucleotide sequence of the gene (selA) and purification of the protein. 200 84

The product of the selA gene, selenocysteine synthase, is a pyridoxal 5-phosphate-containing enzyme which catalyzes the conversion of seryl-tRNA(Sec UCA) into selenocysteyl-tRNA(Sec UCA). Reduction of the aldimine group of pyridoxal 5-phosphate inactivates the enzyme. When reacted with seryl-tRNA(Sec UCA) as sole substrate, pyruvate (and possibly also ammonia) is released; in the presence of a high concentration of potassium borohydride, alanyl-tRNA(Sec UCA) is formed from seryl-tRNA(Sec UCA). These results support the notion that the formyl group of pyridoxal phosphate forms a Schiff base with the alpha-amino group of L-serine with the subsequent 2,3-elimination of a water molecule and the generation of an aminoacrylyl-tRNA(Sec UCA) intermediate. ATP is not required for this reaction step, but it is necessary for the conversion of aminoacrylyl-tRNA into selenocysteyl-tRNA(Sec UCA) which, in addition, requires the SELD protein and reduced selenium. Selenocysteine synthase forms a stable complex with seryl-tRNA(Sec UCA) with one tRNA molecule bound per two 50-kDa monomers. The enzyme does not interact with serine-inserting tRNA species. Taken together, the results show that biosynthesis of selenocysteine takes place in the enzyme-bound state and involves the dehydration of L-serine esterified to tRNA in a first step formally followed by the 2,3-addition of HSe- which is provided by the SELD protein in an ATP-dependent reaction in the form of a reactive selenium donor molecule.
 ...
PMID:Selenocysteine synthase from Escherichia coli. Analysis of the reaction sequence. 200 85

Gale, Glen R. (Veterans Administration Hospital, Durham, N.C.). Urease activity and antibiotic sensitivity of bacteria. J. Bacteriol. 91:499-506. 1966.-An investigation was made of the responses of certain urease-positive bacteria to various antibacterial drugs in the presence of highly specific urease inhibitors, in a test of the hypothesis proposed by other workers that inhibition of bacterial urease enhances the sensitivity of the cells to antimicrobial agents. Urease inhibitors employed were seven hydroxamic acids (HA). Six of the seven HA reduced the sensitivity of nine Proteus strains to ampicillin and methenamine mandelate. Two HA increased the sensitivity to colistin, and six HA increased the sensitivity to kanamycin. Investigation of the mechanism of action of the synergistic effect between kanamycin and HA led to the tentative conclusion that potentiation was mediated through an initial alteration of cell permeability by the aminoglycoside antibiotic which permitted accumulation of each of the six HA into the cell, at which point each interacted with pyridoxal phosphate. The single HA which failed to yield synergism with kanamycin failed to interact with pyridoxal phosphate in a nonenzymatic system; the other six HA produced alterations of the normal ultraviolet absorption spectrum of the coenzyme.
 ...
PMID:Urease activity and antibiotic sensitivity of bacteria. 517 5