Changes in Wall-Bound Phenolic Acids, Phenylalanine and Tyrosine Ammonia-Lyases, and Peroxidases in Developing Durum Wheat Grains (Triticum turgidum L. Var. Durum)

Abstract

Some aspects of phenolic metabolism have been followed during the development of durum wheat grain. Bound ferulic (FA) and p-coumaric (PCA) acids have been extracted after alkaline hydrolysis and quantified by high-performance liquid chromatography. They increased to reach a maximum during the hydrical step and then decreased rapidly during grain dehydratation. Changes in phenylalanine ammonia-lyase (PAL) (E.C. 4.1.1.5) and L-tyrosine ammonia-lyase (TAL) (E.C. 4.3.1.5) activities have been monitored all along the development of the grain. TAL activity was maximal 2 days before PAL, at the beginning of the hydrical step. The presence of a maximal peroxidasic activity at the end of the hydrical step should be linked to the decrease of alkaline-resistant bound forms of FA. These results may suggest a possible role of peroxidase in the progressive changes from ester-linked forms of phenolic acids to insoluble derivatives, resistant to alkaline hydrolysis.