Inhibited enzyme electrodes. Part 3. A sensor for low levels of H2S and HCN.

It is shown that an inhibited enzyme electrode, using cytochrome oxidase, will respond to H2S, HCN and azide ion. For all three inhibitors the kinetics of the inhibiton and recovery processes have been analysed using the theoretical model presented previously (Albery et al., 1990a).

Inhibited enzyme electrodes. Part 2: The kinetics of the cytochrome oxidase system.

An inhibition enzyme electrode to measure toxic gases can be constructed using the respiratory enzyme cytochrome oxidase. The rate of enzyme turnover is followed by reducing cytochrome c on a gold electrode modified with the mediator bis(4-pyridyl) disulphate. The kinetics and mechanism of the system have been measured.

Inhibited enzyme electrodes. Part 1: Theoretical model.

A theoretical model is developed for an electrochemical sensor for toxic substances which works by measuring the inhibition of the enzyme activity. The enzyme is assumed to follow Michaelis-Menten kinetics and the diffusion kinetic equation describing the concentration profile of the enzyme's substrate in the electrolyte layer between the electrode and the membrane covering the electrode is solved. A complete set of analytical solutions is found which corresponds to a number of different rate limiting processes.

Phorbol esters stimulate spermidine/spermine N1-acetyltransferase activity in mitogen-stimulated bovine lymphocytes.

Phorbol 12-myristate-13-acetate (PMA) is shown to induce spermidine/spermine N1-acetyltransferase, a rate-limiting enzyme of polyamine biodegradation, in bovine lymphocytes. When PMA and phytohemagglutinin (PHA) were added simultaneously, the enzyme activity was stimulated synergistically. The ability of phorbol esters to stimulate the enzyme activity was consistent with their tumor-promoting ability.

Effect of sodium butyrate on induction of ornithine decarboxylase activity in phytohemagglutinin-stimulated lymphocytes.

Effect of sodium butyrate on DNA synthesis and the induction of ornithine decarboxylase (EC 4.1.1.