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R B Gregory

Publications and source records attributed to R B Gregory.

44 records · Page 3Linked to original sources
PubMed1981

The regulatory properties of rabbit muscle pyruvate kinase. The effect of pH.

The regulatory behavior of rabbit pyruvate kinase has been studied as a function of pH. The initial velocity of the enzyme-catalysed reaction as a function of ADP concentration was analysed with the exponential model for a regulatory enzyme. The analysis of the exponential model parameters as functions of pH provided pK values of 6.6 and 8.08 for the free enzyme in its fully ADP-bound conformation. By contrast, the binding of ADP to the ADP-free conformation of the free enzyme did not involve groups that ionize within the pH range (6.2-8.5) of these experiments. The results suggest that homotropic allosteric interactions actually alter the mode of ADP binding. The pK values of 6.63 and 9.00 determined from the analysis of V as a function of pH are readily interpreted in terms of a direct phosphoryl-transfer mechanism in which the beta-phosphoryl group of ADP (pK 6.63) acts as the nucleophile and a lysine epsilon-amino group (pK 9.0) acts as the proton donor in the pyruvate kinase reaction.

Adenosine Diphosphate↗
PubMed1981

Exponential model for a two-ligand, regulatory enzyme. Part 1: computer programs for the determination of the model constants from initial velocity data.

The exponential model for a regulatory enzyme with two ligands (either two substrates or one substrate and an effector) provides an expression for the initial velocity of the catalysed reaction in terms of the fractional saturation of the enzyme by each ligand. This paper describes a program which determines the constants of the model from velocity data, measured with respect to the concentrations of the two ligands, when the corresponding fractional saturations are unknown. Listings of the essential routines, written in BASIC, are provided.

Catalysis↗
PubMed1981

Exponential model for a two-ligand, regulatory enzyme. Part 2: Performance tests of the 'INDEXP' computer program for the determination of model constants from initial velocity data. I. Artificial data.

The exponential model for a regulatory enzyme describes the relationship between the initial velocity of the catalysed reaction and the concentration of two ligands. A program, entitled 'INDEXP' has been designed to analyse rate data in terms of the model (Kinderlerer et at., 1981) and, in this report, its performance is examined when presented with artificial data generated from known constants and random, normally distributed error. It is shown that 'INDEXP' is able to recover good estimates of the constants.

Catalysis↗
PubMed1981

Exponential model for a two-ligand, regulatory enzyme. Part 3: Performance tests of INDEXP computer programs for determination of model constants from initial velocity data. 2. Experimental data.

The exponential model for a regulatory enzyme describes the relationship between the initial velocity of the catalysed reaction and the concentration of two ligands. A program, entitled 'INDEXP' has been devised to analyse rate data in terms of the model (Kinderlerer et al., 1981) and, in this report, its performance is examined when presented with experimental initial velocity data taken from the literature. It is shown that the two-ligand exponential model can satisfactorily rationalise experimental data with five linked constants (Ainsworth and Gregory, 1978); as a result the influence of ligand concentrations on the catalysed reactions can be described in rather simple terms.

Animals↗
PubMedDate not supplied

An evaluation of strategies available for the identification of GTP-binding proteins required in intracellular signalling pathways.

Strategies which can be used to elucidate the nature of a GTP-binding regulatory protein (G-protein) involved in an intracellular pathway of interest in the complex environment of the cell are described and evaluated. A desirable strategy is considered to be one in which the first stage indicates a requirement for one or more G-proteins, provides information on whether a monomeric, trimeric or other type of G-protein is involved, and gives some idea of the G-protein sub-class. In the second stage the specific G-protein involved is identified. Approaches available for investigations in the first stage include the use of analogues of GTP and GDP, AlF4-, inhibitors of G-protein isoprenylation, bacterial toxins which covalently modify G-proteins, and the introduction of a purified GDP dissociation inhibitor, GDP exchange and/or GTP-ase activating protein. Identification of the specific G-protein in the second stage can be achieved using anti G-protein antibodies, G-protein-or receptor-derived peptides, antisense G-protein RNA and over-expressed, constitutively-active or dominant-negative G-protein mutants. The correct interpretation of results obtained with GTP and GDP analogues and AlF4- in the first stage is complex and often difficult, and requires a thorough understanding of the functions and mechanisms of activation of G-proteins. Nevertheless, it is important to reach the correct conclusion at this stage since considerable time and expense are usually required for investigations in the second stage.

Animals↗