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.

Multi-factorialin vivostable isotope fractionation: causes, correlations, consequences and applications

“…This behaviour is the basis for the main IFs in the water cycle, to be outlined in detail below. Correspondingly, for example, ammonia volatilisation from manure in fields, the remaining product in the soil is enriched in 15 N and 2 H.…”

“…The assignment of a subject to carnivore, omnivore or vegetarian nutrition is possible by the determination of the δ 18 O value of the p-OH group of L-tyrosine from protein samples [15] and the δ 2 H values of individual amino acids, respectively [272]. Finally, the method of choice for the origin and authenticity characterisation of fragrances and aromas is the pattern analysis by 2 H NMR (reviewed by Schmidt et al [273]).…”

“…The analysed samples vary from bulk plant and animal material [10,11] over individual substances and metabolites [12,13] to defined positions within single molecules [14,15]. Most interesting but often also quite difficult to understand are the reasons, the *Corresponding author.…”

Special Issue dedicated to Professor Hanns-Ludwig Schmidt on the occasion of his 85th birthday

“…Similar approaches were first applied for origin assignment of heroin and cocaine [48,49], and are still widely used to trace the origin of drugs (natural, semi-synthetic or synthetic), explosives and other compounds of forensic interest. The knowledge of the relation Downloaded by [University Library Technische Universität München] at 05:09 23 April 2015 between δ values of proteins in animals and their food discussed above could be used to indicate illegal feeding of meat and bone meal to ruminants [50,51]. From the beginning, H.-L. Schmidt and his group have contributed much to the methodical, theoretical and empirical foundations of this diverse field of stable isotope research.…”