Abstract
Actinoplanes sp. SE50/110 is the wild type of industrial production strains of the fine-chemical acarbose (acarviosyl-maltose), which is used as α-glucosidase inhibitor in the treatment of type II diabetes. Although maltose is an important building block of acarbose, the maltose/maltodextrin metabolism has not been studied in Actinoplanes sp. SE50/110 yet. Bioinformatic analysis located a putative maltase gene amlE (ACSP50_2474, previously named malL; Wendler et al., 2015a), in an operon with an upstream PurR/LacI-type transcriptional regulator gene, named amlR (ACSP50_2475), and a gene downstream (ACSP50_2473) encoding a GGDEF-EAL-domain-containing protein putatively involved in c-di-GMP signaling. Targeted gene deletion mutants of amlE and amlR were constructed by use of the CRISPR/Cas9 technology. By growth experiments and functional assays of ΔamlE, we could show that AmlE is essential for the maltose utilization in Actinoplanes sp. SE50/110. Neither a gene encoding a maltose phosphorylase (MalP) nor MalP enzyme activity were detected in the wild type. By this, the maltose/maltodextrin system appears to be fundamentally different from other described prokaryotic systems. By sequence similarity analysis and functional assays from the species Streptomyces lividans TK23, S. coelicolor A3(2) and S. glaucescens GLA.O, first hints for a widespread lack of MalP and presence of AmlE in the class Actinobacteria were given. Transcription of the aml operon is significantly repressed in the wild type when growing on glucose and repression is absent in an ΔamlR deletion mutant. Although AmlR apparently is a local transcriptional regulator of the aml operon, the ΔamlR strain shows severe growth inhibitions on glucose and – concomitantly – differential transcription of several genes of various functional classes. We ascribe these effects to ACSP50_2473, which is localized downstream of amlE and presumably involved in the metabolism of the second messenger c-di-GMP. It can be assumed, that maltose does not only represent the most important carbon source of Actinoplanes sp. SE50/110, but that its metabolism is coupled to the nucleotide messenger system of c-di-GMP.
Highlights
IntroductionSE50/110 (ATCC 31044) is a natural derivative of SE50, which was isolated from a soil sample during a screening program by the Bayer AG in 1970 (Frommer et al, 1979; Parenti and Coronelli, 1979)
SE50/110 and in Related Species AmlE is localized in a gene cluster together with two further genes (Figure 1): A gene upstream (ACSP50_2475), which is oriented in a head-to-tail orientation and encodes a PurR/LacI-like transcriptional regulator, and a gene downstream (ACSP50_2473) encoding an uncharacterized protein with diguanylate cyclase and phosphodiesterase domain
SE50/110, because it serves as energy supplier on the one hand and as key precursor of the acarbose biosynthesis on the other hand
Summary
SE50/110 (ATCC 31044) is a natural derivative of SE50, which was isolated from a soil sample during a screening program by the Bayer AG in 1970 (Frommer et al, 1979; Parenti and Coronelli, 1979). It was found to be a natural producer of the α-glucosidase inhibitor acarbose, which is used in the treatment of diabetes mellitus (Wehmeier, 2004; Wehmeier and Piepersberg, 2004). After oral application of acarbose, human intestinal α-glucosidases are inhibited, which leads to a retarded release of monosaccharides. The postprandial blood sugar levels in diabetes patients can be substantially decreased, which is beneficial in the context of cardiovascular morbidity (Rosak and Mertes, 2012). Acarbose is composed of a pseudodisaccharide and an α-1,4-glycosidic-bound maltose (Wehmeier and Piepersberg, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
