PRODUCTION OF L-TRYPTOPHAN FROM D,L-5-INDOLYLMETHYLHYDANTOIN BY RESTING CELLS OF A MUTANT OF ARTHROBACTER SPECIES (DSM-3747)

The reaction parameters and the stereospecificity of the enzymatic cleavage of D,L-5-indolylmethylhydantoin in producing L-tryptophan with resting cells of Arthrobacter sp. DSM 3747 were studied. When intact cells were tested, the optimal pH was between 8.5 and 9.0 and the optimal temperature was 50°C. Both, L-N-carbamoylase and hydantoinase could be stabilized over 24 h at 30 and 40°C by the addition of D,L-5-indolylmethylhydantoin. Furthermore, the hydantoinase was stable over 24 h at 50°C by the addition of 0.5 mM Mn2+ ions. The treatment with sodium desoxycholate turned out to be successful in overcoming the poor availability of D,L-5-indolylmethylhydantoin for the cells. The optimal temperature with permeabilized cells decreased to 30°C and therefore ensured a good enzyme stability. While the L-N-carbamoylase proved to be absolutely L-specific, the hydantoinase led to a mixture of enantiomers of N-carbamoyltryptophan. The produced D-N-carbamoyl-tryptophan caused an inhibition of the L-N-carbamoylase. The transformation yield from D,L-5-indolylmethylhydantoin always reached 100%. © 1990.