Molecular cloning of the extracellular endodextranase of Streptococcus salivarius.

摘要: We report the cloning in Escherichia coli of gene encoding an extracellular endodextranase (alpha-1,6-glucanhydrolase, EC 3.2.1.11) from Streptococcus salivarius PC-1. Recombinants a S. PC-1-Lambda ZAP II genomic library specifying dextranase activity were identified as plaques surrounded by zones clearing on blue dextran agar. One such clone, PD1, had 6.3-kb EcoRI fragment insert which encoded 190-kDa protein with activity. The recombinant strain also produced two lower-molecular-mass polypeptides (90 and 70 kDa) that Native was recovered concentrated culture fluids single 110-kDa polypeptide. PD1 phage lysate PC-1 supernatant fluid extract used to measure substrate specificity native forms dextranase, respectively. Analysis these reaction products thin-layer chromatography revealed expected isomaltosaccharide yielded recombinant-specified enzyme but unable resolve larger polysaccharide enzyme. Furthermore, utilized neither substrates nor hydrolysis for growth.