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G A Hamilton

Publications and source records attributed to G A Hamilton.

At least 37 records · Page 2Linked to original sources
PubMed1986

Oxalyl thiolesters and N-oxalylcysteine are normal mammalian metabolites.

A method for the quantitative analysis of N-oxalylcysteine and oxalyl thiolesters (RSCOCOO-) in biological samples is described. These compounds were found in all rat tissues examined (kidney, liver, brain, heart, muscle and fat), with the amount of N-oxalylcysteine ranging up to 18 nmoles/g wet weight and that of oxalyl thiolesters up to 65 nmoles/g wet weight. The identification of such compounds in animal tissues adds further credence to the hypothesis that they may be important metabolic effectors.

Adipose Tissue↗
PubMed1986

L-myo-inosose-1 as a probable intermediate in the reaction catalyzed by myo-inositol oxygenase.

In previous investigations, it was necessary to have Fe(II) and cysteine present in order to assay the catalytic activity of purified hog kidney myo-inositol oxygenase. In the present study it was found that, if this purified nonheme iron enzyme is slowly frozen in solution with glutathione and stored at -20 degrees C, it is fully active in the absence of activators if catalase is present to remove adventitious H2O2. With this simpler assay system it was possible to clarify the effects of several variables on the enzymic reaction. Thus, the maximum velocity is pH-dependent with a maximum around pH 9.5, but the apparent Km for myo-inositol (air atmosphere) remains constant at 5.0 mM throughout a broad pH range. The enzyme is quite specific for its substrate myo-inositol, is very sensitive to oxidants and reductants, but is not affected by a variety of complexing agents, nucleotides, sulfhydryl reagents, etc. In other experiments it was found that L-myo-inosose-1, a potential intermediate in the enzymic reaction, is a potent competitive inhibitor (Ki = 62 microM), while other inososes and a solution thought to contain D-glucodialdehyde, another potential intermediate, are weak inhibitors. Also, both a kinetic deuterium isotope effect (kH/kD = 2.1) and a tritium isotope effect (kH/kT = 7.5) are observed for the enzymic reaction when [1-2H]- and [1-3H]-myo-inositol are used as reactants. These latter results are considered strong evidence that the oxygenase reaction proceeds by a pathway involving L-myo-inosose-1 as an intermediate rather than by an alternative pathway that would have D-glucodialdehyde as the intermediate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Inhibition of the catalytic subunit of phosphorylase phosphatase by oxalyl thioesters and its possible relevance to the mechanism of insulin action.

Oxalyl thioesters, especially S-oxalylglutathione, are shown to be effective inhibitors of the catalytic subunit of phosphorylase phosphatase. The amount of inhibition was found to be time dependent and partially reversed by thiols, thus suggesting that at least part of the inhibition is due to oxalylation of an enzymic thiol group. The possibility that the inhibition of the phosphatase by oxalyl thioesters may be important in vivo and that oxalyl thioesters may be functioning as negative intracellular messengers for insulin is discussed.

Glutathione↗
PubMed1986

Two faces of nurse faculty: teacher and researcher.

The purpose of this paper is to examine three topics related to nurse educators and research productivity. The first section is an analysis and synthesis of what is known about nurse educator involvement in research activities from published studies. The second section is an examination of factors that may enhance or deter nurse educators from engaging in research activities. The focus of the last section is on the relationship between research and teaching quality. Empirical data are examined and recommendations made for nurse faculty.

Educational Status↗
PubMed1984

Thiazolidine-2-carboxylate derivatives formed from glyoxylate and L-cysteine or L-cysteinylglycine as possible physiological substrates for D-aspartate oxidase.

Adducts of glyoxylate with L-cysteine or L-cysteinylglycine were found to be excellent substrates at low concentrations for beef kidney D-aspartate oxidase. Evidence is presented that cis-thiazolidine-2,4-dicarboxylate and its glycine amide are the actual substrates, and that both are converted in the enzymic reaction to 4-substituted thiazoline-2-carboxylates. The results imply that these thiazolidine derivatives are the likely physiological reactants for mammalian D-aspartate oxidase.

Amino Acid Oxidoreductases↗
PubMed1979

Reactions of cysteamine and other amine metabolites with glyoxylate and oxygen catalyzed by mammalian D-amino acid oxidase.

Pig kidney D-amino acid oxidase [D-amino-acid:oxygen oxidoreductase (deaminating), EC 1.4.3.3] catalyzes a rapid uptake of oxygen when high concentrations (50-100 mM) of glyoxylate and the following amines are present under usual assay conditions (pH 8.3): cysteamine, 2-aminoethanol, putrescine, D,L-1-amino-2-propanol, D,L-2-amino-1-propanol, 3-amino-1-propanol, D,L-octopamine, ethylenediamine, and L-cysteine ethyl ester. Notable physiological amines that do not support a rapid O2 reaction under the above conditions include histamine, serotonin, epinephrine, norepinephrine, spermidine, spermine, and cadaverine. A more detailed kinetic investigation of the reactions involving the first four reactive amines listed above indicated that the cysteamine reaction proceeds at a rapid rate even when cysteamine and glyoxylate are present at less than millimolar concentrations, but greater than millimolar concentrations are needed in the other amine reactions in order to observe a reasonable rate. At low concentrations and pH 7.4, the cysteamine-glyoxylate substrate (presumably thiazolidine-2-carboxylic acid) reacts an order of magnitude faster than any other known D-amino acid oxidase substrate. Considerable circumstantial evidence suggests that the reaction involving cysteamine is occurring physiologically, but the reactions of other amines would be occurring in the cell at a very low rate, if at all. It is proposed that the product of the enzymic reaction may be a metabolic effector that can modify the reactivity of proteins or nucleic acids by covalent attachment.

Amines↗