Pleiotropic carbohydrate-positive pseudorevertants have been isolated from a specific class of rho-crp double mutants of Escherichia coli carrying both defective transcription termination protein, rho, and cyclic AMP receptor protein. The modulation of catabolite repression of beta-galactosidase, amylomaltase, and tryptophanase has been studied in the pseudorevertants. It has been found that th...

A series of mutations has been isolated that confer upon amino-acid auxotrophs of Escherichia coli K-12 the ability to grow when fed various D-amino acids. Several distinct systems, mediating cellular use of the D-isomers of leucine, histidine, phenylalanine, tyrosine, tryptophan, isoleucine, and valine, can be mutationally activated. Mutations leading to D-tryptophan use (dadR) all map near pu...

The present paper is the second in a series designed to correlate substrate structure with the kinetic constants of enzyme-catalysed reactions and thus throw light on the nature of the attachment of the substrate to the enzyme. Since the preparation of the first paper (Nath & Rydon, 1954), which describes the influence of structure on the hydrolysis of substituted phenylf-D-glucosides by emulsi...

The loss of tryptophan oxygenase from rat livers after induction by hydrocortisone treatment was studied in living rats, isolated perfused livers, liver slices and cell-free preparations of these livers. Measurements of the enzyme by its activity and as an antigen were parallel except for apparently nonspecific inactivations in some incubations of cell-free preparations and the temporary, early...

The inducible enzyme, cysteine desulfhydrase, was purified from Salmonella fyphimurium to a state of near homogeneity. This enzyme has a very low tryptophanase activity, lacks cystathionase and tryptophan synthetase activities, and appears to be a specific cysteine desulfhydrase. The purified native enzyme has an s20,W of 10.4 and a molecular weight of 229,000 as determined by equilibrium sedim...