title: Assessment of enzymatic methods in the δ18O value determination of the L-tyrosine p-hydroxy group for proof of illegal meat and bone meal feeding to cattle.
abstract: The δ(18)O value of the p-hydroxy group of L-tyrosine depends on the biosynthesis by plants or animals, respectively. In animal proteins it reflects the diet and is therefore an absolute indicator for illegal feeding with meat and bone meal. The aim of this investigation was to perform the positional (18)O determination on L-tyrosine via a one-step enzymatic degradation. Proteins from plants, herbivores, omnivores, and carnivores were characterized by their δ(13)C, δ(15)N, and δ(18)O values, the latter for normalizing the positional δ(18)O values. Their L-tyrosine was degraded by tyrosine phenol lyase to phenol, analyzed as (2,4,6)-tribromophenol. Degradation by tyrosine decarboxylase yielded tyramine. The δ(18)O values of both analytes corresponded to the trophic levels of their sources but were not identical, probably due to an isotope effect on the tyrosine phenol lyase reaction. Availability of the enzyme, easy control of the reaction, and isolation of the analyte are in favor of tyrosine decarboxylase degradation as a routine method.
authors: isolab GmbH, Woelkestrasse 9/I, D-85301 Schweitenkirchen, Germany.
authors: Nicole
authors: N
authors: Tanz
authors: Roland A
authors: RA
authors: Werner
authors: Wolfgang
authors: W
authors: Eisenreich
authors: Hanns-Ludwig
authors: HL
authors: Schmidt
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D001688:Biological Products; D002417:Cattle; D004044:Dietary Proteins / Q000032:analysis; D016643:Encephalopathy, Bovine Spongiform / Q000517:prevention & control / Q000635:transmission; D005506:Food Contamination / Q000032:analysis; D007881:Legislation, Food; D008460:Meat; D008903:Minerals; D010103:Oxygen Isotopes / Q000032:analysis / Q000737:chemistry; D010636:Phenols / Q000737:chemistry / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry* / Q000378:metabolism; D014445:Tyrosine Decarboxylase / Q000378:metabolism; D014447:Tyrosine Phenol-Lyase / Q000378:metabolism
chemical_list: D001688:Biological Products; D004044:Dietary Proteins; D008903:Minerals; D010103:Oxygen Isotopes; D010636:Phenols; D014443:Tyrosine; D014445:Tyrosine Decarboxylase; D014447:Tyrosine Phenol-Lyase; C027762:bone meal