1. The present study was undertaken to investigate the effects of hypobaric hypoxia, equivalent to an altitude of 5500 m, on antioxidant enzymes in rats. 2. Malondialdehyde levels in serum, heart, lung, liver and kidney of hypobaric-hypoxic rats were all significantly higher than in control rats by day 21 of exposure (P < 0 05), indicating increased oxidative stress. 3. Superoxide dismutase (SOD) catalyses the conversion of the superoxide anion to H202 and 02 The concentration of immunoreactive Mn-SOD in the serum of hypobaric-hypoxic rats was raised significantly from day 5 onwards, whereas in liver and lung, it had decreased significantly by day 21 (P < 0 05). 4. Glutathione peroxidase (GSH-Px) catalyses H202 and certain lipid peroxides. By day 21, GSH-Px activity had increased significantly in the heart and lungs, but decreased significantly in the liver (P < 0'05). 5. Catalase catalyses H202. Catalase activity in the liver and kidney of hypobaric-hypoxic rats was significantly decreased on day 1 (P < 0 05) though levels then recovered. 6. Mn-SOD mRNA in the liver of hypobaric-hypoxic rats was induced during the experiment, the effect being exceptionally marked, especially during the first 3 days of exposure to hypobaric hypoxia. 7. These results suggest that the liver may be more vulnerable than the other organs tested to oxidative stress under hypobaric hypoxia.Oxidative stress is an important cause of in-cell damage. Consequently, numerous studies have been published on the effects on the antioxidant systems of conditions in which the level of tissue oxygenation is changed such as: (i) hypoxia

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YcjT is a kojibiose phosphorylase found in Escherichia coli. We found that sucrose was a good acceptor of YcjT in reverse phosphorolysis using β-d-glucose 1-phosphate as a donor. The product was identified as β-d-fructofuranosyl α-d-glucopyranosyl-(1→2)-α-d-glucopyranoside. This sugar was also synthesized from sucrose and maltose using YcjT and maltose phosphorylase and promoted the growth of the probiotic Bifidobacterium breve.

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