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S J Brewer

Publications and source records attributed to S J Brewer.

13 recordsLinked to original sources
PubMed1984

Chemical synthesis and cloning of a poly(arginine)-coding gene fragment designed to aid polypeptide purification.

A 43-bp DNA duplex coding for poly(arginine) [poly(arg)] has been synthesised by modified phosphotriester procedures. It has been inserted into the Bg/II and BamHI restriction sites of a cloned synthetic beta-urogastrone (Uro) gene, under the control of the trp promoter. Subsequent induction with 3 beta-indole acrylic acid produces beta-Uro with a C-terminal poly(arg) fusion. The raised isoelectric point of this polypeptide fusion facilitates rapid purification by cation exchange chromatography. The C-terminal poly(arg) tail can be readily removed by treatment with carboxypeptidase B.

Arginine↗
PubMed1980

An adenosine triphosphate-dependent carbamoylphosphate--3-hydroxymethylcephem O-carbamoyltransferase from Streptomyces clavuligerus.

Cell-free supernatants from cells of Streptomyces clavuligerus (N.R.R.L. 3585), which are actively synthesizing cephamycin C, transfer a carbamoyl group from carbamoylphosphate to a 3-hydroxymethylceph-3-em-4-carboxylic acid nucleus to form a 3-carbamoyloxymethylcephem. This reaction was stimulated by nucleoside triphosphates and by a mixture of Mn2+ and Mg2+ cations. The enzyme responsible was purified 40-fold by batch absorption onto DEAE-cellulose and hydroxyapatite. The purified O-carbamoyltransferase is most active at pH 6.8. It is stabilized by phosphate anions, but is inhibited by PPi anions, (NH4)2SO4 or NaCl. The enzyme is stimulated by ATP, but it is not known whether this nucleotide acts as an effector or as a substrate. Some activity is observed with dATP, but two other analogues of ATP, in which a methylene group replaced the oxygen atom between the alpha- and beta- or the beta- and gamma-phosphorus atoms, inhibit the action of ATP itself. The enzyme synthesizes a wide range of 3-carbamoyloxymethylcephems. The structure of some of these products, for example that of cefuroxime (3-carbamoyloxymethyl-7 beta-[2-(fur-2-yl)-2-syn-methoxyiminoacetamido]ceph-3-em-4-carboxylic acid), was confirmed by their proton-n.m.r. spectra.

Adenosine Triphosphate↗
PubMed1978

The oxygenation of [3-methyl-3H]desacetoxycephalosporin C [7beta-(5-D-aminadipamido)-3-methylceph-3-em-4-carboxylic acid] to [3-hydroxymethyl-3H]desacetylcephalosporin C by 2-oxoglutarate-linked dioxygenases from Acremonium chrysogenum and Streptomyces clavuligerus.

Cell-free extracts of Acremonium chrysogenum and Streptomyces clavuligerus oxidize the 3-methyl group of desacetoxycephalosporin C to a 3-hydroxymethyl group. The enzyme responsible for this reaction in these organisms was purified 20- and 30-fold respectively by chromatography on DEAE-cellulose. The enzymes, which were assayed with [3-methyl-3H]desacetoxycephalosporin C as substrate, have the properties expected of 2-oxoglutarate-linked dioxygenases. They require 2-oxoglutarate, Fe2+ cations and a mixture of reducing agents (dithiothreitol and ascorbate) for full activity. The enzyme from A. chrysogenum, but not that S. clavuligerus, is activated about 10-fold when it is preincubated with a reaction mixture from which either desacetoxycephalosporin C or 2-oxoglutarate is omitted. Fe2+ cations seem to play a key role in this activation. Both enzymes seem highly specific for cephalosporins with the natural 7beta-(5-D-aminoadipamido) side chain and are likely to be responsible for the oxidation of the 3-methylcephem nucleus in vivo.

Cephalosporins↗
PubMed1973

Control of the production of exo-beta-N-acetylglucosaminidase by Bacillus subtilis B.

1. The control of exo-beta-N-acetylglucosaminidase (EC 3.2.1.30) production by Bacillus subtilis B growing on a chemically defined medium was studied. 2. The enzyme was repressed during exponential growth by those carbon sources that enter the glycolytic pathway above the level of phosphoenolpyruvate. When exponential growth ceased as a result of low concentrations of the nitrogen, carbon or metal ion components of the medium, the enzyme was formed and its amount could be increased by the addition of cell-wall fragments as inducer. 3. The enzyme was de-repressed and could be induced during exponential growth on non-glycolytic compounds metabolized directly into pyruvate, acetyl-CoA or tricarboxylic acid cycle intermediates. 4. The major difference in the metabolism of the organism utilizing these two groups of compound was the existence of high activities of phosphoenolpyruvate carboxylase required for gluconeogenesis. 5. It is concluded that the de-repression of glucosaminidase occurs when the only principal change detected in the intermediary metabolism of the organism was the presence of high activities of phosphoenolpyruvate carboxylase. 6. When the organism was grown on media containing repressing compounds, the enzyme was only de-repressed on entry of the cells into the initial stages of sporulation, where phosphoenolpyruvate carboxylase activity, even in the presence of excess of glucose, increased in parallel with glucosaminidase, neutral proteinase and alkaline phosphatase activities. 7. These results suggest a strong link, at the level of the tricarboxylic acid cycle, between the control of phosphoenolpyruvate carboxylase and the control of the de-repression of glucosaminidase and sporulation.

Acetamides↗