| Budget Amount *help |
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
We are studying the mechanisms of the NADPH oxidase system responsible for anti-infectious activity of phagocytes. Patients with chronic granulomatous disease (CGD), a genetic disorder in this system, fail to generate superoxide anion and suffer from recurrent infections.
1.Gp91, the redox center of the NADPH oxidase, had been considered to contain both heme and FAD in its molecule. However, this flavocytochrome concept was only based on the similarities between the amino acid sequences of gp91 and other flavoproteins, without any direct evidence. The main reason for this was that most of the mutations in gp91 lead complete absence of its protein. We discovered a rare CGD patient who expressed a gp91 apoprotein. Analysis of cDNA revealed the mutation of His-338 to Try, which resided in a predicted domain for FAD-binding. The biochemical analysis of the patient revealed that the lost FAD completely, and the addition of reagent FAD in vitro could not corrected his superoxide-generating activity. These resulted indicate that His-338 is a very critical for FAD incorporation into the NADPH oxidase. This was the first such mutation found in CGD.
2. There have not been studies, which inquired the NADPH oxidase in relation to microorganism-derived toxins. Here, we investigated the effect of gliotoxin from Aspergillus on the NADPH oxidase. This toxin, bearing S-S bond in its structure, prevented the onset of superoxide generation by the neutrophil NADPH oxidase in response to PMA. Gliotoxin affected the activation process, but not the catalysis of the activated enzyme. The inhibitory mode was suggested to be direct interaction of S-S bond in gliotoxin with vicinal SH group in the NADPH oxidase.
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