GlnR and PhoP directly regulate the transcription of genes encoding starch-degrading, amylolytic enzymes in Saccharopolyspora erythraea.

ABSTRACT: Starch-degrading enzymes hydrolyze starch- and starch-derived oligosaccharides to yield glucose. We investigated the transcriptional regulation of genes encoding starch-degrading enzymes in the industrial actinobacteria Saccharopolyspora erythraea We observed that most genes encoding amylolytic enzymes (one ?-amylase, one glucoamylase and four ?-glucosidases) were regulated by GlnR and PhoP, which are global regulators of nitrogen and phosphate metabolism, respectively. Electrophoretic mobility shift assays and RT-PCR analyses demonstrated that GlnR and PhoP directly interact with their promoter regions, and collaboratively or competitively activate their transcription. Deletion of glnR caused poor growth on starch, maltodextrin, and maltose, whereas overexpression of glnR and phoP increased the total activity of ?-glucosidase resulting in enhanced carbohydrate utilization. Additionally, transcript levels of amylolytic genes and total glucosidase activity were induced in response to nitrogen and phosphate limitation. Furthermore, regulatory effects of GlnR and PhoP on starch-degrading enzymes were conserved in Streptomyces coelicolor A3 (2). These results demonstrate that GlnR and PhoP are involved in polysaccharide degradation by mediating the interplay among carbon, nitrogen, and phosphate metabolism in response to cellular nutritional states. Our study reveals a novel regulatory mechanism underlying carbohydrate metabolism, and suggests new possibilities for designing genetic engineering approaches to improve the utilization rate of starch in actinobacteria.

SUBMITTER: Xu Y 

PROVIDER: S-EPMC5103082 | biostudies-other | 2016 Sep

REPOSITORIES: biostudies-other