Role of NADH-cytochrome b(5) reductase in biosynthesis of thyroid hydrogen peroxide / 生理学报

The activity of NADH-cytochrome b(5) reductase (b(5)R) and the levels of hydrogen peroxide in the thyroid of patients with Graves' disease (GD) and normal controls were measured with potassium ferricyanide as substrate and with the homovanillic acid fluorescence assay. The activity of b(5)R and the level of H2O2 in GD thyroid were definitely higher than those in normal control, but the activity of catalase in GD thyroid was not significantly different from that in normal thyroid. After addition of p-chloromercuribenzoate, a b(5)R inhibitor, the activity of b(5)R in GD and normal thyroid decreased by 85%, the level of H2O2 decreased by 50%, and protein-bound iodine (PBI) formation by 52%. There is a positive correlation between the level of H2O2 and the activity of b(5)R. Our data indicate that b(5)R participates in thyroid hydrogen peroxide biosynthesis, and is an important enzyme in the production of H2O2.

Metabolic Flux Analysis of L-Arginine Fermentation in Corynebacterium glutamicum / 微生物学通报

In this paper, metabolic networks of the Corynebacterium glutamicum GWY020 and the two de-rivatives carrying additional mutations HUI821and GUI089 were established and modified. The concentra-tions of extra-cellular metabolites were determined under sub-steady-state (50 h~52 h) of the batch culture. The metabolic flux distribution maps of the three strains were obtained, compared and analyzed. These re-sults indicate that the introduction of analog supersensitive marker or analog resistant marker skew the metabolic flux towards the formation of L-Arginine. This study revealed the usefulness of the metabolic flux analysis as a tool for verification of existing production strains. The analysis may play an important role in helping us to rationally re-design metabolism for further improvement of fermentation process.