Holotryptophanase in the presence of K+ undergoes a pHdependent change (pK 7.2) from a protonated, enzymatically inactive form (EH), X,,, 420 rnp, to a deprotonated, active form (S), X,,, 337 mp. Only the inactive form appears when K+, which is required for activity, is replaced by Na+ or imidazole. Both forms of the enzyme are completely inactivated by borohydride reduction, indicating that ea...

The name tryptophanase was given by Happold & Hoyle (1935) to the enzyme complex of Escherichia coli which induces and catalyzes the production of indole from tryptophan by non-viable bacterial preparations with the consumption of five atoms of oxygen (Woods, 1935). The present communication describes the preparation of this complex in the cell-free state, and subsequent investigation of the co...

A mutant of Escherichia coli that lacks leucyl-, phenylalanyl-transfer ribonucleic acid-protein transferase had diminished activities of L-phenylalanyl-transfer ribonucleic acid synthetase and tryptophanase, grew faster than its parent with aspartic acid as the sole nitrogen source, accumulated higher levels of enterochelin in the medium during iron limitation, and exhibited an abnormal morphol...

We used site-directed mutagenesis to replace the Escherichia coli tryptophanase (tna) operon leader peptide start codon with AUC. This change greatly decreased the uninduced rate of tna operon expression, and it also lowered the response to inducer. We conclude that leader peptide synthesis plays an essential role in tna operon expression.

The facts described by Happold &'Hoyle [1936] and Evans et al. [1941] can be concisely stated as follows: (1) In a complex medium (e.g. bouillon, casein-digest, etc.) in which the presence of glucose in sufficient amount inhibits completely the production of indole by B. coli, the complete tryptophanase system is absent from the cells. (2) With a simple salt medium as used by Fildes, glucose on...

2. There are specific repressor effects: galactose is an effective repressor for ,B-galactosidase but not for the other enzymes; conversely, pyruvate represses tryptophanase and serine deaminase but not ,-galactosidase. 3. In wild-type E. coli glucose represses all three enzymes. A mutant has been selected in which there is no glucose effect for any of the enzymes but in which each enzyme remai...