DI-ISODITYROSINE, A NOVEL TETRAMERIC DERIVATIVE OF TYROSINE IN PLANT-CELL WALL PROTEINS - A NEW POTENTIAL CROSS-LINK

A novel amino acid, di-isodityrosine, has been isolated from hydrolysa tes of cell walls of tomato cell culture. Analysis by UV spectrometry, partial derivatization with 2,4-dinitrofluorobenzene and mass and NMR spectrometry show that the compound is composed to two molecules of i sodityrosine, joined by a biphenyl linkage. The possible reactions inv olved in the formation of this molecule in vivo are discussed, as is t he possibility that it could form an interpolypeptide linkage between cell wall proteins such as extensin, and hence aid in the insolubiliza tion of the protein in the wall.