کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1178199 | 962673 | 2010 | 12 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Molecular identification of unsaturated uronate reductase prerequisite for alginate metabolism in Sphingomonas sp. A1 Molecular identification of unsaturated uronate reductase prerequisite for alginate metabolism in Sphingomonas sp. A1](/preview/png/1178199.png)
In Sphingomonas sp. A1, alginate is degraded by alginate lyases to its constituent monosaccharides, which are nonenzymatically converted to an α-keto acid, namely, 4-deoxy-l-erythro-5-hexoseulose uronic acid (DEH). The properties of the DEH-metabolizing enzyme and its gene in strain A1 were characterized. In the presence of alginate, strain A1 cells inducibly produced an NADPH-dependent DEH reductase (A1-R) in their cytoplasm. Molecular cloning of the enzyme gene indicated that A1-R belonged to the short-chain dehydrogenase/reductase superfamily and catalyzed the conversion of DEH to 2-keto-3-deoxy-d-gluconic acid most efficiently at around pH 7.0 and 50 °C. Crystal structures of A1-R and its complex with NADP were determined at around 1.6 Å resolution by X-ray crystallography. The enzyme consists of three layers (α/β/α), with a coenzyme-binding Rossmann fold. NADP is surrounded by positively charged residues, and Gly-38 and Arg-39 are crucial for NADP binding. Site-directed mutagenesis studies suggest that Ser-150, Tyr-164, and Lys-168 located around the Rossmann fold constitute the catalytic triad. To our knowledge, this is the first report on molecular cloning and structure determination of a bacterial DEH reductase responsible for alginate metabolism.
Journal: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics - Volume 1804, Issue 9, September 2010, Pages 1925–1936