title: Two distinct types of mutations conferring to Escherichia coli K12 capability of D-tryptophan utilization.
abstract: We showed that the ability of Escherichia coli K12 tryptophan auxotrophs to utilize D-tryptophan as a substitute for L-tryptophan may result from two types of mutations. The first type consisted in changes in the dadR regulatory site of the dad operon increasing the synthesis of D-amino acid dehydrogenase. The mutations of the second type mapped within the dad A structural gene. They changed the apparent substrate specificity of D-amino acid dehydrogenase. We suppose that the change may be due to an altered enzyme structure which make it more accessible to D-tryptophan.
mesh_terms: D000409:Alanine / Q000378:metabolism; D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D002874:Chromosome Mapping; D003641:Deamination; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D005798:Genes, Bacterial; D009154:Mutation; D009876:Operon; D010641:Phenotype; D013379:Substrate Specificity; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D014364:Tryptophan; D000594:Amino Acid Oxidoreductases; D000409:Alanine