胃幽門螺旋桿菌26695菌株之D型阿拉伯糖-5-磷酸異構酶由HP1429基因所表現之特性研究

Characterization of Helicobacter pylori 26695 D-arabinose 5-phosphate isomerase encoded by HP1429

林義心(Yee-Shin Lim)

指導教授 ： 高茂傑

國立清華大學/生命科學院/分子醫學研究所/碩士(2008年)

https://doi.org/10.6843/NTHU.2008.00128

摘要

Helicobacter pylori (H. pylori) is a major pathogen residing in human stomach. Chronic infection of this bacterium can cause gastric ulcer, duodenal ulcer, gastric cancer and mucosa-associated lymphoid tissue (MALT) lymphoma. The outer membrane of H. pylori anchors the lipopolysaccharide (LPS) which is present in many Gram-negative bacteria. LPS not only contributes to the structural integrity of the outer membrane but also induces immune responses from the host cells. The interaction between LPS and the host cell is believed to be related to disease development. Bioinformatic studies on the open reading frame of HP1429 suggested that the product of this gene may be involved in the synthesis of a conserved molecule 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) which is present in the core oligosaccharide region of the LPS and is also the building block of the polysialic acid capsule. The Kdo biosynthesis starts with the conversion of a pentose pathway intermediate D-ribulose 5-phosphate (Ru5P) to D-arabinose 5-phosphate (A5P), and the reaction is catalyzed by an D-arabinose 5-phosphate isomerase (API). In this study, HP1429 was cloned, overexpressed and the functions of the gene product were characterized. The purified recombinant HP1429 protein has a molecular weight of 37,814 Dalton, and appears to be a tetramer. This protein has an optimal activity at pH 7.0, and is sensitive to inhibition by zinc cations with an estimated IC50 of 30 - 50 μM. This enzyme is specific for interconversion of A5P and Ru5P, with apparent Km values of 0.97 ± 0.18 mM for A5P and 0.46 ± 0.02 mM for Ru5P. The apparent kcat in the A5P to Ru5P direction is 179.3 ± 3.3 s-1 and 74.5 ± 1.6 s-1 in the Ru5P to A5P direction. The equilibrium constant (Keq) is 0.50 (Ru5P/A5P). Homology search showed that HP1429 might be the only gene coding for API in H. pylori 26695 strain.

關鍵字

胃幽門螺旋桿菌 ； D型阿拉伯糖-5-磷酸異構? ； HP1429 ； 脂多醣類

並列摘要

無資料

並列關鍵字

Helicobacter pylori ； D-arabinose 5-phosphate isomerase ； HP1429 ； lipopolysaccharide

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