title: The gac-gene cluster for the production of acarbose from Streptomyces glaucescens GLA.O: identification, isolation and characterization.
abstract: The C7N-cyclitol containing alpha-glucosidase inhibitor acarbose is commercially produced using developed strains of Actinoplanes and is used in the treatment of patients suffering from diabetes type II. We have identified a second acarbose production cluster using a genomic cosmid gene bank from Streptomyces glaucescens GLA.O and sequenced a region (42658bp; accession AM409314) which clearly contained a gene cluster (gac-cluster) for the synthesis of acarbose or acarbose related endproducts. The gac-cluster exhibited large similarities to the acb-gene cluster from Actinoplanes. However, remarkable differences are found in the biosynthesis of the C7N-cyclitol in the two acarbose biosynthesis pathways. We show the expression of selected genes using RT-PCR approaches, we were able to detect small amounts of acarbose or acarbose related metabolites and we have characterized the GacK protein, an acarbose kinase, which specifically phosphorylates acarbose and acarbose homologs. All these data in combination with the postulated functions of the encoded Gac proteins clearly indicate that also in S. glaucescens a recycling mechanism for acarbose ("carbophor") which had been described for the first time for acarbose cluster from Actinoplanes, is also realised.
authors.affiliation: Bergische Universität Wuppertal, Institute for Chemical Microbiology, Wuppertal, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Rockser
authors.forename: Udo F
authors.initials: UF
authors.lastname: Wehmeier
mesh_terms: D020909:Acarbose / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D054812:Cyclitols / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2; D015870:Gene Expression; D005798:Genes, Bacterial; D065089:Glycoside Hydrolase Inhibitors; D026901:Membrane Transport Proteins / Q000235:genetics; D053858:Metabolic Networks and Pathways / Q000235:genetics; D005810:Multigene Family; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013302:Streptomyces / Q000235:genetics / Q000378:metabolism; D000516:alpha-Amylases / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D054812:Cyclitols; D065089:Glycoside Hydrolase Inhibitors; D026901:Membrane Transport Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); C101444:acarbose 7-phosphotransferase; D000516:alpha-Amylases; D020909:Acarbose