EC Number   |
General Information |
Reference |
|---|
    4.1.99.1 | evolution |
enzyme Trpase is classified as beta-eliminating lyase |
746654 |
| 4.1.99.1 | evolution |
residue Phe464 in Escherichia coli TIL is homologous to Phe459 in Proteus vulgaris TIL |
746632 |
| 4.1.99.1 | evolution |
the carbon-carbon lyases, tryptophan indole lyase (TIL) and tyrosine phenol-lyase (TPL, EC 4.1.99.2) are bacterial enzymes which catalyze the reversible elimination of indole and phenol from L-tryptophan and L-tyrosine, respectively. These pyridoxal 5'-phosphate-dependent enzymes show high sequence homology (about 40% identity) and both form homotetrameric structures. Pre-steady state kinetics with TPL and TIL show rapid formation of external aldimine intermediates, followed by deprotonation to give quinonoid intermediates absorbing at about 500 nm. The active sites of TIL and TPL are highly conserved with the exceptions of these residues: Arg381(TPL)/Ile396 (TIL), Thr124 (TPL)/Asp137 (TIL), and Phe448 (TPL)/His463 (TIL). The conserved tyrosine, Tyr71 (TPL)/Tyr74 (TIL) is essential for elimination activity with both enzymes, and likely plays a role as a proton donor to the leaving group. A unique feature of TIL and TPL is another strictly conserved lysine immediately preceding the pyridoxal 5'-phosphate-binding lysine, and hydrogen bonded to a water molecule bound to the monovalent cation. The mechanisms of TPL and TIL require both substrate strain and acid/base catalysis, and substrate strain is probably responsible for the very high substrate specificity of TPL and TIL. Both enzymes require a monovalent cation, either K+, NH4+, Rb+ or Cs+ for activity, with Na+ and Li+ giving little or no activity. The active site residues involved in PLP binding are highly conserved for both TIL and TPL. Sequence comparisons |
747245 |
| 4.1.99.1 | malfunction |
a truncated TnaA protein containing only domains D1 and D3 (D1D3) localizes to the cell pole. Mutations affecting the D1D3-to-D1D3 interface do not affect polar localization of D1D3 but do delay assembly of wild-type TnaA foci. In contrast, alterations to the D1D3-to-D2 domain interface produce diffuse localization of the D1D3 variant but do not affect the wild-type protein. Altering several surface-exposed residues decreases TnaA activity, implying that tetramer assembly may depend on interactions involving these sites. Changing any of three amino acids at the base of a loop near the catalytic pocket decreases TnaA activity and causes it to form elongated ovoid foci in vivo, indicating that the alterations affect focus formation and may regulate how frequently tryptophan reaches the active site. Mutant phenotypes, detailed overview |
747414 |
| 4.1.99.1 | metabolism |
indole production requires TnaB responsible for exogenous L-tryptophan import |
-, 728262 |
| 4.1.99.1 | metabolism |
tryptophanase is an initial enzyme for the degradation of L-tryptophan and 5-hydroxytryptophan in Escherichia coli |
726660 |
| 4.1.99.1 | more |
determination of residues that affect assembly and localization of TnaA foci, overview |
747414 |
| 4.1.99.1 | more |
eight catalytically important residues Thr52, Tyr74, Arg103, Asp137, Arg230, Lys269, Lys270, and His463 are located close to the Trpase active site and are absolutely conserved in Trpases. Five of them are located in the conserved regions and are reported to confer a crucial role for binding of the substrate and cofactor to produce the formation of the best intermediate that will lead to substrate degradation. Despite the apparent diversity in the protein sequences, these regions may be essential for enzyme activity to generate indole, which is an important agent for bacterial physiology, ecological balance, and virulence |
-, 746778 |
| 4.1.99.1 | more |
the conformation of all holo subunits is the same in both crystal forms. The structures suggest that Trpase is flexible in the apoform. Its conformation partially closes upon binding of PLP. The closed conformation might correspond to the enzyme in its active state with both cofactor and substrate bound in a similar way as in tyrosine phenol-lyase |
746654 |
| 4.1.99.1 | more |
the conserved Phe449 in TPL locates within 3 A of the substrate aromatic ring in the closed conformation |
747245 |
