D-p-Hydroxyphenylglycine production from dl-5-p-hydroxyphenylhydantoin by Agrobacterium sp.

Abstract

A bacterium that stereospecifically produces D-p-hydroxyphenylglycine (D-PHPG) from DL-5-p-hydroxyphenylhydantoin (DL-5-PHPH) was isolated from soil and identified as Agrobacterium sp. IP-I 671. The hydantoinase and the N-carbamyl-amino acid amido-hydrolase involved in this biotransformation process were both strictly D-stereospecific. Their biosynthesis was found to be inducible by addition of 2-thiouracil to the cultivation media, or to a lesser extent by uracil. The amidohydrolase activity of Agrobacterium sp. was strongly inhibited by ammonium ions co-produced with D-PHPG, whereas the hydantoinase activity under the same conditions was unaffected. Optimum temperature and pH were respectively 55° C and 10 for the partially purified hydantoinase, 45° and 6.75 when resting cells were used. Biotransformation under these slightly acidic conditions allowed to complete conversion of 30 g/1 DL-5-PHPH into 25 g/l of D-PHPG (molar yield 96%) and involved enzymatic racemization of DL-5-PHPH.