Lima André O S, Quecine Maria C, Fungaro Maria H P, Andreote Fernando D, Maccheroni Walter, Araújo Welington L, Silva-Filho Márcio C, Pizzirani-Kleiner Aline A, Azevedo João L
Departamento de Genética, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Av. Pádua Dias 11, Piracicaba, SP, 13418-900, Brazil.
Appl Microbiol Biotechnol. 2005 Jul;68(1):57-65. doi: 10.1007/s00253-004-1740-1. Epub 2004 Nov 6.
Endophytes comprise mainly microorganisms that colonize inner plant tissues, often living with the host in a symbiotic manner. Several ecological roles have been assigned to endophytic fungi and bacteria, such as antibiosis to phytopathogenic agents and plant growth promotion. Nowadays, endophytes are viewed as a new source of genes, proteins and biochemical compounds that may be used to improve industrial processes. In this study, the gene EglA was cloned from a citrus endophytic Bacillus strain. The EglA encodes a beta-1,4-endoglucanase capable of hydrolyzing cellulose under in vitro conditions. The predicted protein, EglA, has high homology to other bacterial cellulases and shows a modular structure containing a catalytic domain of the glycosyl hydrolase family 9 (GH9) and a cellulose-binding module type 3 (CBM3). The enzyme was expressed in Escherichia coli, purified to homogeneity, and characterized. EglA has an optimum pH range of 5-8, and remarkable heat stability, retaining more than 85% activity even after a 24-h incubation at pH 6-8.6. This characteristic is an important feature for further applications of this enzyme in biotechnological processes in which temperatures of 50-60 degrees C are required over long incubation periods.
内生菌主要由定殖于植物内部组织的微生物组成，通常与宿主以共生方式生活。内生真菌和细菌具有多种生态功能，如对植物病原体的抗菌作用和促进植物生长。如今，内生菌被视为可用于改进工业生产过程的新基因、蛋白质和生化化合物来源。在本研究中，从一株柑橘内生芽孢杆菌菌株中克隆了EglA基因。EglA编码一种能够在体外条件下水解纤维素的β-1,4-内切葡聚糖酶。预测的蛋白质EglA与其他细菌纤维素酶具有高度同源性，并显示出一种模块化结构，包含糖基水解酶家族9（GH9）的催化结构域和3型纤维素结合模块（CBM3）。该酶在大肠杆菌中表达，纯化至同质，并进行了特性鉴定。EglA的最适pH范围为5-8，具有显著的热稳定性，即使在pH 6-8.6下孵育24小时后仍保留超过85%的活性。这一特性对于该酶在生物技术过程中的进一步应用具有重要意义，在这些过程中，需要在50-60摄氏度的温度下长时间孵育。
