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首页> 外文期刊>Infection and immunity >Neuraminidase production by a Streptococcus sanguis strain associated with subacute bacterial endocarditis.
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Neuraminidase production by a Streptococcus sanguis strain associated with subacute bacterial endocarditis.

机译：血链球菌菌株与亚急性细菌性心内膜炎相关的神经氨酸酶产生。

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摘要

The properties of an extracellular neuraminidase produced by a Streptococcus sanguis strain (isolated from a confirmed case of subacute bacterial endocarditis) during growth in a defined medium was examined in this investigation. This enzyme, isolated from concentrated culture supernatants of S. sanguis biotype II, was active against human alpha-1 acid glycoprotein, N-acetylneuramin lactose, bovine submaxillary mucin, and fetuin. Neuraminidase production paralleled bacterial growth in defined medium and was maximal in the early stationary phase of growth but decreased dramatically, probably owing to protease production, during the late stationary phase. The enzyme was purified to near homogeneity by a combination of salt fractionation, ion-exchanged chromatography on DEAE-Sephacel, and gel filtration on Sephadex G-200. These procedures yielded an enzyme preparation that possessed a specific activity of 174.4 mumol of sialic acid released per min per mg of protein against human alpha-1 acid glycoprotein. The Km value for this enzyme with human alpha-1 acid glycoprotein as substrate was 2.5 X 10(-3) M, and the enzyme possessed a pH optimum of 6.5. The S. sanguis neuraminidase had a molecular weight of approximately 85,000 as estimated by gel filtration and approximately 90,000 when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was stable at temperatures of 4 and 37 degrees C for 3 h, but approximately 50% of the enzymatic activity was lost within 30 min at 50 degrees C, with 100% of the enzymatic activity being destroyed within 10 min at temperatures of greater than or equal to 65 degrees C.
机译：在这项研究中，研究了由血链球菌菌株（从确诊的亚急性细菌性心内膜炎病例中分离）在特定培养基中生长期间产生的细胞外神经氨酸酶的特性。这种酶是从浓缩的S.sanguis生物型II培养上清液中分离出来的，对人α-1酸性糖蛋白，N-乙酰神经氨酸乳糖，牛下颌粘蛋白和胎球蛋白具有活性。神经氨酸酶的产生与特定培养基中细菌的生长平行，并且在生长的早期固定阶段最大，但在静止后期则可能由于蛋白酶的产生而急剧下降。通过盐分馏，DEAE-Sephacel上的离子交换色谱和Sephadex G-200上的凝胶过滤的组合，将酶纯化至接近均一。这些程序产生了一种酶制剂，该酶制剂具有每分钟每毫克蛋白质释放的针对人α-1酸糖蛋白的174.4微摩尔唾液酸的比活性。以人α-1酸性糖蛋白为底物的该酶的Km值为2.5 X 10（-3）M，该酶的最适pH为6.5。通过凝胶过滤估计，桑氏葡萄球菌神经氨酸酶的分子量约为85,000，而通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析，分子量约为90,000。该酶在4和37摄氏度的温度下稳定3小时，但在50摄氏度的30分钟内约有50％的酶活性丧失，而在更高温度下的10分钟内100％的酶活性被破坏。等于或等于65摄氏度。

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