Molecular Biology Department, National Research Center, 33-El Bohouthst., Dokki P.O.12622, Gieza, Egypt.
Microbial Chemistry Department, National Research Center, 33-El Bohouthst., Dokki P.O.12622, Giza, Egypt.
Int J Biol Macromol. 2020 Apr 1;148:292-301. doi: 10.1016/j.ijbiomac.2020.01.120. Epub 2020 Jan 13.
Different bacterial isolates with amylolytic activity were insulated from various honey samples. The most active isolate was identified by the molecular 16SrRNA sequence technique as Bacillus atrophaeus NRC1. The bacterium showed maximum amylase production under optimum culture conditions at pH 6.0, 40 °C and after 24 h incubation. Two amylase isoenzymes (AmyI and AmyII) from Bacillus atrophaeus NRC1 have been purified to homogeneity by using ammonium sulfate precipitation, Sephacryl S-200 and DEAE-Sepharose chromatography. The major isoenzyme, AmyI, had a specific activity 4635 U/mg proteins with molecular weight of 61 kDa using SDS-PAGE electrophoresis. The maximum activity of AmyI against starch was determined at pH 6.0 and 50 °C. AmyI was stable up to 50 °C after incubation for 30 min, retained 65 and 23% of its activity at 60 and 70 °C, respectively. Pre-incubation with Ca, Mg and Ba cations for 30 min enhanced the enzyme activity; while it was completely inhibited by Hg. Varied inhibition degree of the enzyme activity was determined with K, Ni, Zn, Na and Cu ions. AmyI was inhibited by EDTA, PMSF and SDS, while it was activated by l-Cysteine-HCl and DTT. AmyI had the ability to degrade starch, amylopectin, glycogen, amylose and lacked the affinity towards β-1,4-linked xyloses.
从各种蜂蜜样本中分离出具有淀粉水解活性的不同细菌分离株。通过分子 16SrRNA 序列技术鉴定最活跃的分离株为萎缩芽孢杆菌 NRC1。该细菌在最佳培养条件下(pH 6.0、40°C 和 24 小时孵育后)表现出最大的淀粉酶产量。从萎缩芽孢杆菌 NRC1 中纯化出两种淀粉酶同工酶(AmyI 和 AmyII),通过硫酸铵沉淀、Sephacryl S-200 和 DEAE-Sepharose 层析达到均一性。主要同工酶 AmyI 的比活为 4635 U/mg 蛋白,分子量为 61 kDa,使用 SDS-PAGE 电泳。AmyI 对淀粉的最大活性在 pH 6.0 和 50°C 下确定。AmyI 在 50°C 孵育 30 分钟后保持高达 50°C 的稳定性,在 60°C 和 70°C 下分别保留其活性的 65%和 23%。30 分钟的预孵育可增强 Ca、Mg 和 Ba 阳离子对酶活性的影响;而 Hg 则完全抑制了酶活性。用 K、Ni、Zn、Na 和 Cu 离子测定了酶活性的不同抑制程度。AmyI 被 EDTA、PMSF 和 SDS 抑制,而被 l-Cysteine-HCl 和 DTT 激活。AmyI 具有降解淀粉、支链淀粉、糖原、直链淀粉的能力,且对β-1,4 连接的木糖没有亲和力。
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