No abstract

Euglena gracilis lacks a catalase and contains a single APX (ascorbate peroxidase) and enzymes related to the redox cycle of ascorbate in the cytosol. In the present study, a full-length cDNA clone encoding the Euglena APX was isolated and found to contain an open reading frame encoding a protein of 649 amino acids with a calculated molecular mass of 70.5 kDa. Interestingly, the enzyme consisted of two entirely homologous catalytic domains, designated APX-N and APX-C, and an 102 amino acid extension in the N-terminal region, which had a typical class II signal proposed for plastid targeting in Euglena. A computer-assisted analysis indicated a novel protein structure with an intramolecular dimeric structure. The analysis of cell fractionation showed that the APX protein is distributed in the cytosol, but not the plastids, suggesting that Euglena APX becomes mature in the cytosol after processing of the precursor. The kinetics of the recombinant mature FL (full-length)-APX and the APX-N and APX-C domains with ascorbate and H2O2 were almost the same as that of the native enzyme. However, the substrate specificity of the mature FL-APX and the native enzyme was different from that of APX-N and APX-C. The mature FL-APX, but not the truncated forms, could reduce alkyl hydroperoxides, suggesting that the dimeric structure is correlated with substrate recognition. In Euglena cells transfected with double-stranded RNA, the silencing of APX expression resulted in a significant increase in the cellular level of H2O2, indicating the physiological importance of APX to the metabolism of H2O2.

Lung age could be used to motivate lifestyle change in obese individuals.

Sclerosing mediastinitis is not a common condition in the thoracic cavity and is difficult to cure. Several medications have been used; however, most of the cases do not achieve satisfactory results, and the most successful treatment is operative resection. We report the first case of IgG4-related sclerosing mediastinitis that showed IgG4-positive plasma cells infiltrated into the fibrous tissue and a high serum IgG4 level. The patient clearly showed remission of the symptoms after steroid therapy. Our findings suggest that the serum IgG4 level is a good selection indicator for steroid therapy in sclerosing mediastinitis.

D-Galacturonic acid reductase, a key enzyme in ascorbate biosynthesis, was purified to homogeneity from Euglena gracilis. The enzyme was a monomer with a molecular mass of 38-39 kDa, as judged by SDS-PAGE and gel filtration. Apparently it utilized NADPH with a Km value of 62.5+/-4.5 microM and uronic acids, such as D-galacturonic acid (Km=3.79+/-0.5 mM) and D-glucuronic acid (Km=4.67+/-0.6 mM). It failed to catalyze the reverse reaction with L-galactonic acid and NADP(+). The optimal pH for the reduction of D-galacturonic acid was 7.2. The enzyme was activated 45.6% by 0.1 mM H(2)O(2), suggesting that enzyme activity is regulated by cellular redox status. No feedback regulation of the enzyme activity by L-galactono-1,4-lactone or ascorbate was observed. N-terminal amino acid sequence analysis revealed that the enzyme is closely related to the malate dehydrogenase families.

Ascorbate is an abundant and indispensable redox compound in plants. Genetic and biochemical studies have established the D-mannose/L-galactose (D-Man/L-Gal) pathway as the predominant ascorbate biosynthetic pathway in streptophytes, while the D-galacturonate (D-GalUA) pathway is found in prasinophytes and euglenoids. Based on the presence of the complete set of genes encoding enzymes involved in the D-Man/L-Gal pathway and an orthologous gene encoding aldonolactonase (ALase)a key enzyme for the D-GalUA pathway -Physcomitrium patens may possess both pathways. Here, we have characterized the moss ALase as a functional lactonase and evaluated the ascorbate biosynthesis capability of the two pathways using knockout mutants. Physcomitrium patens expresses two ALase paralogs, namely PpALase1 and PpALase2. Kinetic analyses with recombinant enzymes indicated that PpALase1 is a functional enzyme catalyzing the conversion of L-galactonic acid to the final precursor L-galactono-1,4-lactone and that it also reacts with dehydroascorbate as a substrate. Interestingly, mutants lacking PpALase1 (Dal1) showed 1.2fold higher total ascorbate content than the wild type, and their dehydroascorbate content was increased by 50% compared with that of the wild type. In contrast, the total ascorbate content of mutants lacking PpVTC2-1 (Dvtc2-1) or PpVTC2-2 (Dvtc2-2), which encode the rate-limiting enzyme GDP-L-Gal phosphorylase in the D-Man/L-Gal pathway, was markedly decreased to 46 and 17%, respectively, compared with that of the wild type. Taken together, the dominant ascorbate biosynthetic pathway in P. patens is the D-Man/L-Gal pathway, not the D-GalUA pathway, and PpALase1 may play a significant role in ascorbate metabolism by facilitating dehydroascorbate degradation rather than ascorbate biosynthesis.

No abstract

Including this case, only four of the 17 reported cases of congenital cholesteatoma of the mastoid region showed post-auricular pain or swelling, indicating acute mastoiditis. Clinicians should bear in mind that congenital cholesteatoma may be present in patients presenting with mastoiditis, particularly adults.