Hydroxylation of phenylalanine by Pseudomonas sp.: measurement of an isotope effect following the NIH shift
Abstract
The conversion of [4-3H]- and [4-3H;3,5-2H2]phenylalanine into tyrosine by cultures of Pseudomonas sp. (ATCC 11 299a) has been studied. Comparison of the tritium retentions observed during hydroxylation of the two precursors showed an isotope effect, kD/kT= 2·8 ± 0·1 (kH/kD= 10 ± 1), for the final aromatisation reaction following the NIH shift. This value is compared with those of likely chemical models for the biochemical process.