Lin S B, Stutzenberger F J
Department of Microbiology, Clemson University, SC, USA.
J Appl Bacteriol. 1995 Oct;79(4):447-53. doi: 10.1111/j.1365-2672.1995.tb03160.x.
The major beta-1,4-endoglucanase (EG) of the thermophilic actinomycete, Thermomonospora curvata, contributed over 80% of the total EG activity recovered from cell-free culture fluid after growth on cellulose. The enzyme was purified to electrophoretic homogeneity by ammonium sulphate precipitation, ion-exchange chromatography and size exclusion HPLC. This monomeric enzyme had a specific activity of 750 IU mg(-1) when assayed with 2.5% (w/v) carboxymethyl cellulose (CMC) at 70 degrees C, pH 6.0. Highest activity was observed on CMC with a degree of polymerization of 3200. The EG was stable for 48 h at 60 degrees C, pH 6.0 and had a half-life of 30 min at 80 degrees C; temperature and pH optima were 70-73 degrees C and 6.0-6.5, respectively. The mol. wt was 100,000 and the pI was 4.0. The Km and Vmax values were 7.33 mg/ml(-1) and 833 microns min(-1), respectively. EG activity was inhibited by Fe(2+), Hg(2+), Ag(+) and Pb(2+), and enhanced by dithiothreitol and Zn(2+). The first 12 amino acid residues at the N-terminus were: Asp-Glu-Val-Asp-Glu-Ile-Arg-Asn-Gly-Asp-Phe-Ser. Glutamic and aspartic acid constituted 24% of the total amino acid composition; no amino sugar was found.
嗜热放线菌弯曲高温单孢菌的主要β-1,4-内切葡聚糖酶（EG），在以纤维素为生长底物的无细胞培养液中，其活性占总EG活性的80%以上。通过硫酸铵沉淀、离子交换色谱和尺寸排阻高效液相色谱法，将该酶纯化至电泳纯。当在70℃、pH 6.0条件下用2.5%（w/v）的羧甲基纤维素（CMC）测定时，这种单体酶的比活性为750 IU mg⁻¹。在聚合度为3200的CMC上观察到最高活性。该EG在60℃、pH 6.0条件下稳定48小时，在80℃下半衰期为30分钟；最适温度和pH分别为70 - 73℃和6.0 - 6.5。分子量为100,000，等电点为4.0。Km和Vmax值分别为7.33 mg/ml⁻¹和833 μmol min⁻¹。EG活性受到Fe²⁺、Hg²⁺、Ag⁺和Pb²⁺的抑制，而二硫苏糖醇和Zn²⁺则增强其活性。N端的前12个氨基酸残基为：Asp-Glu-Val-Asp-Glu-Ile-Arg-Asn-Gly-Asp-Phe-Ser。谷氨酸和天冬氨酸占总氨基酸组成的24%；未发现氨基糖。
