Is Helicobacter pylori a risk factor for NSAID-associated gastric ulcer bleeding? A sex- and age-matched case-control study

中國醫藥大學機構典藏 China Medical University Repository, Taiwan > 中國醫藥大學 > 期刊論文 > Item 310903500/28644

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题名:	Is Helicobacter pylori a risk factor for NSAID-associated gastric ulcer bleeding? A sex- and age-matched case-control study
作者:	Wu, CY;Poon, SK;Chen, GH
贡献者:	中國醫藥大學;China Med Coll, Taichung Vet Gen Hosp, Dept Internal Med, Gastroenterol Sect, Taichung 407, Taiwan
日期:	1998
上传时间:	2010-09-24 13:39:01 (UTC+8)
出版者:	HEALTH COMMUNICATIONS INC
摘要:	N-Acetyltransferase (NAT), responsible for bioactivation and detoxification of arylamines, has been demonstrated to be widely distributed in many organisms ranging from humans to microorganisms. Using high performance liquid chromatography (HPLC) to analyze NAT activity in bacteria, the authors found that Pseudomonas aeruginosa exhibited high NAT activity with 2-aminofluorene (2-AF) as substrate. Characteristics of this bacterial NAT were further investigated. The N-acetylation catalyzed by this enzyme is an acetyl coenzyme A (AcCoA)-dependent reaction. As the concentration of AcCoA in the reaction mixture was increased, the apparent K-m and V-max for 2-AF increased. The K-m and V-max were 0.504 +/- 0.056 mM and 31.92 +/- 3.23 nmol/min/mg protein, respectively, for the acetylation of 2-AF with 0.5 mM AcCoA. The optimum pH for the enzyme activity was estimated to be around 8.5. It was active at a temperature range from 5 degrees C to 55 degrees C, with maximum activity at 37 degrees C. The enzyme activity was inhibited by divalent metal ions including Cu++, Fe++, Zn++, Ca++, Co++, Mn++, and Mg++, suggesting that a sulfhydryl group is involved in the N-acetylation activity. The three chemical modification agents, iodoacetamide, phenylglyoxal, and diethylpyrocarbonate, all exhibited a dose-, time-, and temperature-dependent inhibition effect. Preincubation of the NAT with AcCoA provided significant protection against the inhibition of iodoacetamide and diethylpyrocarbonate, but only partial protection against the inhibition of phenylglyoxal. These results indicate that cysteine, histidine, and arginine residues are essential for this bacterial enzyme activity, and the first two are likely to reside on the AcCoA binding site, but arginine residue may be located only near the AcCoA binding site. Our data demonstrate that P. aeruginosa possesses highly active N-acetyltransferase which shares a similar catalytic mechanism as that of higher organisms. These findings are very helpful for further investigating the role of arylamine NAT in this bacterial species.
關聯:	ADVANCES IN THERAPY 15(2):85-91
显示于类别:	[中國醫藥大學] 期刊論文

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