A bacterial trehalose phosphorylase (TPase; EC 2.4.1.64) was purified from the culture supernatant of Bacillus stearothermophilus SK-1 to apparent homogeneity, and some properties were investigated. Furthermore, a gene from SK-1 responsible for the TPase was cloned by Southern hybridization with a degenerate oligonucleotide probe synthesized on the basis of the N-terminal sequence of the purified enzyme. The Mr of the enzyme was estimated to be 150,000 by gel filtration and 83,000 by SDS-PAGE, so the enzyme is likely to be a homodimer. The enzyme had optimum activity at pH 7.0-8.0 or nearby and the optimum temperature was about 75°C. The deduced amino acid sequence of the SK-1 TPase encodes a theoretical protein with a Mr of 87,950. Alignment of amino acid sequences with a maltose phosphorylase from Lactobacillus brevis the crystal structure and active site of which had been analyzed suggested that these two phosphorylases evolved from a common ancestor. The Escherichia coli cells harboring the plasmid containing the cloned TPase gene had about 100 times the activity of SK-1.
从嗜热芽孢杆菌 SK-1 的培养上清液中纯化了一种细菌
海藻糖磷酸化酶(TPase;
EC 2.4.1.64)至明显的同质性,并对其一些特性进行了研究。此外,利用基于纯化酶 N 端序列合成的退化寡核苷酸探针,通过南方杂交技术克隆了一个与 TPase 相关的 SK-1
基因。通过凝胶过滤法估计该酶的相对分子质量为 150,000,而通过
SDS-PAGE 估计为 83,000,因此该酶可能是一个同源二聚体。该酶在 pH 7.0-8.0 或附近具有最佳活性,最佳温度约为 75°C。SK-1 TPase 的推测
氨基酸序列编码的理论蛋白质相对分子质量为 87,950。与已分析其晶体结构和活性位点的
乳酸菌
麦芽糖磷酸化酶的
氨基酸序列比对表明,这两种
磷酸化酶源自一个共同的祖先。转化了包含克隆 TPase
基因质粒的大肠杆菌细胞,其活性约为 SK-1 的 100 倍。