The mechanisms of action of ethanolamine ammonia-lyase, an adenosylcobalamin-dependent enzyme. Evidence that carbon-cobalt bond cleavage is driven in part by conformational alterations of the corrin ring.

Previous work has shown that the interaction between ethanolamine ammonia-lyase (ethanolamine ammonia-lyase, EC 4.3.1.

Solubilization of the O2(-)-forming activity responsible for the respiratory burst in human neutrophils.

On exposure to suitable activating agents, neutrophils sharply alter their oxygen metabolism, showing large increases in oxygen uptake, O2 and H2O2 production, and glucose consumption via the hexose monophosphate shunt. These metabolic alterations, which together are designated the "respiratory burst," are due to the activation of a system which catalyzes the reaction: 2O2 + NADPH leads to 2O2(-) + NADP. This O2(-)-forming system is found in a particulate fraction isolated from neutrophils which had been activated with opsonized zymosan.

Termination of the respiratory burst in human neutrophils.

Recent evidence has suggested that a particulate O(2) (-)-forming system is responsible for the respiratory burst in activated neutrophils. The respiratory burst is normally a transient event, lasting only 30-60 min. To investigate the mechanism by which the burst is terminated, we examined the O(2) (-)-forming activity of neutrophil particles as a function of time in the presence and absence of agents known to affect the function of intact cells.

Superoxide-forming enzyme from human neutrophils: evidence for a flavin requirement.

The superoxide-forming activity of 27,000-g particles prepared from homogenates of zymosan-treated human neutrophils is lost if the assay is conducted in the presence of 0.045% Triton X-100. This loss in activity in the presence of detergent is prevented by 40 micron flavin adenine dinucleotide (FAD), but not by flavin mononucleotide, riboflavin, adenosine 5'-diphosphate, or adenosine 5'-monophosphate.

Oxidation of epinephrine by a cell-free system from human granulocytes.

Homogenates of normal human granulocytes were found to catalyze the oxidation of epinephrine to adrenochrome. This reaction was abolished by superoxide dismutase and catalase, but not by albumin or boiled dismutase, indicating that epinephrine oxidation was dependent on O2- AND H2O2. Elimination experiments to identify the electron donor for O2- production showed that the reaction was not inhibited by gel filtration of the homogenate or by removal of glucose, sucrose, or phosphate from the reaction mixture, raising the possibility that epinephrine itself was the reducing agent for the production of O2-.

Defect in pyridine nucleotide dependent superoxide production by a particulate fraction from the granulocytes of patients with chronic granulomatous disease.

Particulate fractions from normal human granulocytes preactivated with opsonized zymosan were found to catalyze superoxide production in the presence of reduced pyridine nucleotides. Similar preparations from three patients with X-linked chronic granulomatous disease produced no detectable superoxide. The failure to produce superoxide was not due to an inhibitor, since cell-free preparations from the patients' granulocytes had no effect on superoxide production by normal particles.

Biological defense mechanisms. Evidence for the participation of superoxide in bacterial killing by xanthine oxidase.

Incubation of either Staphylococcus epidermidis or Escherichia coli with a sufficiently high concentration of xanthine oxidase, an enzyme capable of reducing oxygen to superoxide (O2-), resulted in the death of the microorganisms. Protection against the killing os S. epidermidis by xanthine oxidase was afforded by superoxide dismutase, an enzyme which converts O2- to O2 and H2O2, and also by catalase, which destroys H2O2.

Biological defense mechanisms. The production by leukocytes of superoxide, a potential bactericidal agent.

As a highly reactive substance produced in biological systems by the one-electron reduction of oxygen, superoxide (O(2) (-)) seemed a likely candidate as a bactericidal agent in leukocytes. The reduction of cytochrome c, a process in which O(2) (-) may serve as an electron donor, was found to occur when the cytochrome was incubated with leukocytes. O(2) (-) was identified as the agent responsible for the leukocyte-mediated reduction of cytochrome c by the demonstration that the reaction was abolished by superoxide dismutase, an enzyme that destroys O(2) (-), but not by boiled dismutase, albumin, or catalase.

Stimulation of mitochondrial adenosine diphosphate uptake by thyroid hormones.

Thyroid hormone administered in vivo increased carrier-mediated (atractyloside-sensitive) ADP uptake by rat liver mitochondria. 3 Days after a single large dose of triiodothyronine (20 mug/100 g of body weight), mitochondrial uptake of ADP measured at 6 degrees was 2.35 +/- 0.