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B E Davidson

Publications and source records attributed to B E Davidson.

101 records · Page 6Linked to original sources
PubMed1971

Purification and properties of 3-deoxy-d-arabinoheptulosonic acid-7-phosphate synthetase (phe) from a lambda aroG+ transductant of Escherichia coli.

By incorporating aroG, the structural gene for 3-deoxy-d-arabinoheptulosonic acid-7-phosphate (DAHP) synthetase (phe), into the genome of a heat-inducible susR60 mutant of phage lambda, it has been possible to increase the intracellular levels of DAHP synthetase (phe) in a lysogenized strain of Escherichia coli some 15-fold over levels found in the wild-type strain. By using this strain, the enzyme has been purified approximately 2,000-fold compared with wild type, and various kinetic parameters of the purified enzyme have been studied. In contrast to previous reports, the inhibition by phenylalanine was found to exhibit sigmoidal kinetics, suggestive of cooperative interactions between phenylalanine binding sites. Stimulation of enzyme activity by Co(2+) was minimal (14%).

Aldehyde-Lyases↗
PubMed1967

The reactivity of the disulphide bonds of purified proteins in relationship to primary structure.

1. With the aid of a coupled system involving glutathione reductase, the reaction of glutathione with the disulphide bonds of purified proteins has been studied. 2. Bovine serum albumin, conalbumin, lysozyme, trypsin inhibitors from egg white, lima bean and soya bean either did not react with glutathione or reacted only slightly. With these proteins reactivity was markedly increased by limited proteolysis. 3. Bovine and human gamma-globulins, fibrinogen and beta-lactoglobulin exhibited some reactivity (less than 15%) with glutathione and again this was increased by limited proteolysis. Pepsin, trypsin and chymotrypsin exhibited greater reactivity than the proteins previously mentioned. Di-isopropylphosphoryl-chymotrypsin exhibited less reactivity than chymotrypsin, suggesting that autolysis under the experimental conditions used contributed towards the reactivity of this protein. Proteolysis also increased the reactivity of these proteins. The three disulphide bonds of insulin were reduced by glutathione. 4. Above 35 degrees the disulphide bonds of serum albumin show a progressive increase in reactivity and at 55 degrees half of the bonds become accessible to glutathione. 5. From the results obtained with the proteins investigated, the conclusion reached is that the disulphide bonds of native proteins are structurally protected and do not react with glutathione under physiological conditions.

Animals↗
PubMed1967

Reduction of ribonuclease by glutathione at elevated temperatures: the molecular mechanism.

1. The mechanism of the reaction between ribonuclease and GSH at elevated temperatures has been studied by using N-(4-dimethylamino-3,5-dinitrophenyl)-maleimide to label the reduced ribonuclease. 2. After incubation for 2hr. at 35 degrees , enzymically active ribonuclease was recovered; at 50.8 degrees half of the initial ribonuclease was recovered as enzymically active ribonuclease and half as reduced labelled ribonuclease; at 55 degrees all of the initial ribonuclease was recovered in the labelled form. 3. It was inferred that the rate-limiting step was the reduction of the first disulphide bond in any one molecule. This was followed by rapid reduction of the other bonds in the same molecule.

Amino Acids↗
PubMed1965

The reactivity of the disulphide bonds of bovine pancreatic ribonuclease with glutathione.

1. Bovine pancreatic ribonuclease is not reduced by GSH at near-physiological concentrations and pH. 2. Disruption of the structure of ribonuclease by proteolytic enzymes leads to products that can be reduced by GSH. 3. At higher temperatures the disulphide bonds of ribonuclease are completely reduced by GSH in a coupled system. The T(tr) is 51 degrees and this has been found to be lower than the T(tr) for the abnormal tyrosine residues under the same conditions.

Animals↗