Departamento de Bioquímica e Imunologia, Faculdade de Medicina e Imunologia de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil.
Folia Microbiol (Praha). 2013 Nov;58(6):615-21. doi: 10.1007/s12223-013-0249-3. Epub 2013 Apr 24.
A thermotolerant fungus identified as Aspergillus niveus was isolated from decomposing materials and it has produced excellent levels of hydrolytic enzymes that degrade plant cell walls. A. niveus germinated faster at 40 °C, presenting protein levels almost twofold higher than at 25 °C. The crude extract of the A. niveus culture was purified by diethylaminoethyl (DEAE)-cellulose, followed by Biogel P-100 column. Polygalacturonase (PG) is a glycoprotein with 37.7 % carbohydrate, molecular mass of 102.6 kDa, and isoelectric point of 5.4. The optimum temperature and pH were 50 °C and 4.0-6.5, respectively. The enzyme was stable at pH 3.0 to 9.0 for 24 h. The DEAE-cellulose derivative was about sixfold more stable at 60 °C than the free enzyme. Moreover, the monoaminoethyl-N-aminoethyl-agarose derivative was tenfold more stable than the free enzyme. PG was 232 % activated by Mn(2+). The hydrolysis product of sodium polypectate corresponded at monogalacturonic acid, which classifies the enzyme as an exo-PG. The K m, V max, K cat, and K cat/K m values were 6.7 mg/ml, 230 U/mg, 393.3/s, and 58.7 mg/ml/s, respectively. The N-terminal amino acid sequence presented 80 % identity with PglB1, PglA2, and PglA3 putative exo-PG of Aspergillus fumigatus and an exo-PG Neosartorya fischeri.
从分解物中分离出一种名为白僵菌的耐热真菌，它能产生高水平的水解酶，可降解植物细胞壁。白僵菌在 40°C 时发芽更快，蛋白质水平几乎是 25°C 时的两倍。白僵菌培养物的粗提物通过二乙氨基乙基（DEAE）-纤维素进行纯化，然后通过 Biogel P-100 柱进行纯化。聚半乳糖醛酸酶（PG）是一种糖蛋白，含糖量为 37.7%，分子量为 102.6 kDa，等电点为 5.4。最适温度和 pH 值分别为 50°C 和 4.0-6.5。该酶在 pH 3.0 至 9.0 下 24 小时稳定。DEAE-纤维素衍生物在 60°C 下比游离酶稳定约六倍。此外，单氨基乙基-N-氨基乙基琼脂糖衍生物比游离酶稳定十倍。PG 被 Mn(2+) 激活 232%。聚半乳糖酸钠的水解产物与单半乳糖醛酸相对应，这将该酶归类为外切 PG。K m、V max、K cat 和 K cat/K m 值分别为 6.7 mg/ml、230 U/mg、393.3/s 和 58.7 mg/ml/s。N 端氨基酸序列与烟曲霉的 PglB1、PglA2 和 PglA3 假定外切 PG 以及 Neosartorya fischeri 的外切 PG 具有 80%的同源性。
