Käfer E, Tittler A, Fraser M J
Department of Biology, McGill University, Montreal, Canada.
Biochem Genet. 1989 Apr;27(3-4):153-66. doi: 10.1007/BF02401798.
High levels of nuclease activities were identified in filtrates of Aspergillus cultures after growth in low-but not in high-phosphate media. Deoxyribonuclease activities, characterized extensively by column chromatography, showed a coincident single peak for ss- and ds-DNase which was distinct from the peak for RNase. Both ss-DNase and ds-DNase are endonucleolytic and showed the highest activity in the presence of Ca2+ and Mn2+ (at pH 8.0). They also showed identical heat sensitivities suggesting that a single, phosphate-repressible DNase was secreted. This enzyme, therefore, corresponds to the well-characterized extracellular DNase A of Neurospora. However, the Aspergillus DNase A did not cross-react with antisera to secreted Neurospora nucleases and showed different chromatographic properties, and active peptides of different sizes were visualized on DNA activity gels. The increasing derepression of Aspergillus DNase A by decreasing phosphate levels was similar to that of secreted alkaline phosphatase and these increases were both abolished by the regulatory mutant palcA.
在低磷培养基（而非高磷培养基）中生长后，曲霉培养滤液中鉴定出高水平的核酸酶活性。通过柱色谱广泛表征的脱氧核糖核酸酶活性显示，单链和双链脱氧核糖核酸酶有一个重合的单峰，这与核糖核酸酶的峰不同。单链脱氧核糖核酸酶和双链脱氧核糖核酸酶均为内切核酸酶，在Ca2+和Mn2+存在下（pH 8.0）活性最高。它们还表现出相同的热敏感性，表明分泌的是一种单一的、受磷酸盐抑制的脱氧核糖核酸酶。因此，这种酶对应于已充分表征的粗糙脉孢菌细胞外脱氧核糖核酸酶A。然而，曲霉脱氧核糖核酸酶A与针对粗糙脉孢菌分泌核酸酶的抗血清无交叉反应，且表现出不同的色谱特性，在DNA活性凝胶上可见不同大小的活性肽段。随着磷酸盐水平降低，曲霉脱氧核糖核酸酶A的去抑制作用增强，这与分泌型碱性磷酸酶相似，而这两种增加均被调节突变体palcA消除。
