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A A Jacobs

Publications and source records attributed to A A Jacobs.

52 records · Page 3Linked to original sources
PubMed1971

Role of the Phagocyte in Host-Parasite Interactions XXVII. Myeloperoxidase-H(2)O(2)-Cl-Mediated Aldehyde Formation and Its Relationship to Antimicrobial Activity.

Evidence is presented which suggests that the mechanism of action of the myeloperoxidase-H(2)O(2)-Cl(-) antimicrobial system in the phagocyte is by the formation of aldehydes. Aldehyde production resulting from myeloperoxidase-mediated decarboxylation and deamination of alanine was quantitated with 20,000-g granules from guinea pig polymorphonuclear leukocytes serving as the enzyme. Equimolar quantities of acetaldehyde and CO(2) were obtained. There was an absolute requirement for both H(2)O(2) and Cl(-) for decarboxylation by the myeloperoxidase-containing granules. The myeloperoxidase-H(2)O(2)-Cl(-) system decarboxylated both d- or l-alanine equally and had a pH optimum of 5.3. Decarboxylation of l-alanine by intact guinea pig polymorphonuclear leukocytes was increased 2.5-fold by phagocytosis. Guaiacol peroxidation by the granules was inhibited 90% in the presence of Cl(-) at acid pH. Under these conditions, decarboxylation and deamination of amino acids by myeloperoxidase were significantly stimulated, resulting in aldehyde production. Taurine, a competitive inhibitor of amino acid decarboxylation, inhibited bactericidal activity of the myeloperoxidase-H(2)O(2)-Cl(-) system but had no effect on the myeloperoxidase-H(2)O(2)-I(-) bactericidal system. Since the myeloperoxidase-H(2)O(2)-I(-) system does not participate in amino acid decarboxylation, its mechanism of antimicrobial action appears to be different from that found with Cl(-).

Journal Article↗
PubMed1970

Function of h(2)o(2), myeloperoxidase, and hexose monophosphate shunt enzymes in phagocytizing cells from different species.

The effect of phagocytosis on the H(2)O(2) production and myeloperoxidase (MPO) activities of leukocytes from various species was investigated. The intracellular distribution of MPO, reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase (6PGDH) of resting and phagocytizing guinea pig polymorphonuclear leukocytes has also been studied. Phagocytizing cells produce more H(2)O(2) than the corresponding resting cells. This has been found to be true for human peripheral polymorphonuclear leukocytes, mouse peritoneal macrophage, and guinea pig and rat peritoneal polymorphonuclear leukocytes. All of these cells, except rabbit alveolar macrophages, have significant MPO activity. Generally an increased activity is noted with phagocytizing cells. Homogenization and differential centrifugation of guinea pig peritoneal polymorphonuclear leukocytes indicate that the whole homogenate and its fractions from phagocytizing cells have significantly higher MPO and NADPH oxidase activities, when compared to the corresponding fractions from the resting cells. The 27,000 x g supernatant fluid from phagocytizing cells has 6-fold more MPO and 2.5-fold more NADPH oxidase activity than similar supernatant fractions from resting cells. The enzyme 6PGDH was unaffected by phagocytosis. The relationship of these stimulated activities to the intracellular bactericidal function of the phagocytes has been discussed.

Journal Article↗
PubMed1970

Role of the Phagocyte in Host-Parasite Interactions XXIV. Aldehyde Generation by the Myeloperoxidase-H(2)O(2)-Chloride Antimicrobial System: a Possible In Vivo Mechanism of Action.

Myeloperoxidase (MPO), H(2)O(2), and chloride ions in the presence of bacteria form aldehydes and are bactericidal. The use of heat-inactivated MPO prevented both killing and aldehyde generation. Decarboxylation and deamination of carboxyl and amino group substrates arising from the bacterial surface may participate in the reaction which yields aldehydes. Bacterial contact was essential for killing. Decarboxylation and bactericidal activities were noted when physiological concentrations of chloride were used. When MPO was replaced with horseradish peroxidase (HPO) in the chloride medium, decarboxylation and bactericidal activities were no longer noted. In contrast, iodide functioned in the antimicrobial system with either MPO or HPO. The iodide concentrations required were at least sixfold greater than circulating blood iodide levels. Moreover, decarboxylation did not occur in the presence of iodide with either enzyme. Thus, both halides function in the MPO-H(2)O(2) system but by different mechanisms. It is likely that in vivo under most conditions chloride is the functional halide and that generation of aldehydes is the mechanism responsible for the antimicrobial activity of the MPO-H(2)O(2)-chloride system.

Journal Article↗