芽胞杆菌BSD-8肌氨酸氧化酶的纯化与性质

Purification and characterization of a sarcosine oxidase from Bacillus sp. BSD-8

摘要:

对一株从土壤中分离到的芽胞杆菌Bacillus sp. BSD-8菌株所产生的热稳定性较高的肌氨酸氧化酶进行纯化，并对该酶的特性进行了研究。通过硫酸铵分级沉淀、DEAE-纤维素离子交换柱、Toyopearl疏水层析柱和Sephadex G-75分子筛层析，使酶提纯25倍，比活力达到5.3 U/mg。研究了纯化后的酶的生化特性，确定了该酶的主要特性：该酶为黄素蛋白，与黄素以非共价键的方式结合，由单一亚基组成，其亚基分子量为51 kDa。酶的最适反应温度及pH分别为60℃与8.5。该酶在60℃及pH 8.0~10.0条件下稳定。以Lineveaver-Burk作图法求得该酶米氏常数Km值为3.1 mmol/L。Ag+、Hg2+、SDS及 Tween 80对该酶有强抑制作用，而Tween 20和Triton X-100对酶活性无影响。该肌氨酸氧化酶在耐热性质上比以前所报道的肌氨酸氧化酶有很大的提高，在酶法肌酐测定应用中有明显的优势。

Abstract:

We purified a sarcosine oxidase from Bacillus sp. strain BSD-8 isolated from soil. We purified the enzyme by ammonium sulfate precipitation, DEAE-cellulose, Toyopearl hydrophobic and Sephadex G-75 molecular sieve chromatography and characterized the purified sarcosine oxidase. This sarcosine oxidase was a flavin enzyme containing a noncovalently bound flavin with the subunit molecular mass of 51 kDa. The optimal temperature for this enzyme was 60?C and it showed its highest activity at pH 8.5. It was stable in the pH range of 8.0–10.0 and at the temperature of 60?C. Estimated by Lineveaver-Burk plots, the Km of the enzyme was 3.1 mmol/L. Ag+, Hg2+, SDS and Tween 80 dramatically inhibted the enzyme activity, whereas Tween 20 and Triton X-100 had no effect on enzyme activity. The thermostability of this enzyme was better than reported sarcosine oxidases, and it could be applied in enzymatic measuring of creatinine.