Occurrence of an Inducib } e Phenylserine Isolated from Soil Dehydratase inPseutlomonas pickettii PS 22 '

Although 3-phenylserine, which is an antagonist of phenylalanine, has been known to be degraded by phenylserine aidolase,i) serine hydroxymethyltransferase,2) and L-amino acid oxidase,i) little attention has been paid to the metabolism of 3-phenylserine in microorganisms. We have found that D-threo-3-phenylserine was a better substrate for NADP'-dependent D-threonine dehydrogenase [EC 1.1.1.-] ftom Pseudomenas cruciviae IFO 1 2047.4) To use fbr the preparation of D-threo-3-phenylserine from the DL form, we screened for soil bacteria that use L-threo-3phenylserine as a sole carbon and nitrogen source and found an inducible dehydratase, whi ¢ h catalyzes the conversion of L-threo3-phenylserineintophenylpyruvateandammonia,inabacterium. This paper describes the occurrence of a novel L-threo-3phenylserine dehydratase in the crude extract of Pseudomonas pickettii PS22 isolated from soil. L-threo-3-Phenylserine-assirnilating bacteria wcre isolated from