Catalytic studies on tryptophanase from Bacillus alvei.
Tryptophanase from Bacillus alvei exhibited the expected spectrum of pyridoxal-5'-phosphate-dependent reactions. It exhibited l-serine dehydratase, S-alkyl-cysteine lyase, and cysteine desulfhydrase activities, as well as the classic tryptophanase reactions (all beta elimination reactions). It also acted as a tryptophan synthetase (beta replacement reactions) using indole plus l-serine or l-cysteine or S-methyl-cysteine as substrates. The beta elimination reactions are simple competitors of the replacement reactions for the same amino acid substrates. The kinetics of the reactions were examined in detail using a coupled continuous spectrophotometric assay. A product (indole) inhibition study of the beta elimination reaction with tryptophan showed simple, noncompetitive inhibition; the same study with allosubstrates showed noncompetitive inhibition by indole. These product studies provided data on the beta replacement reactions as well. The results are discussed in terms of a mechanism for the B. alvei tryptophanase.
D001407:Bacillus / Q000201:enzymology*; D003545:Cysteine; D006836:Hydro-Lyases / Q000378:metabolism*; D007211:Indoles / Q000494:pharmacology; D007700:Kinetics; D012695:L-Serine Dehydratase / Q000378:metabolism; D011773:Pyruvates / Q000096:biosynthesis; D012694:Serine; D013053:Spectrophotometry; D014364:Tryptophan / Q000096:biosynthesis; D014367:Tryptophan Synthase / Q000378:metabolism; D014368:Tryptophanase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism
D007211:Indoles; D011773:Pyruvates; D012694:Serine; D014364:Tryptophan; D014368:Tryptophanase; D006836:Hydro-Lyases; D014367:Tryptophan Synthase; D012695:L-Serine Dehydratase; D003545:Cysteine