PULCHEROSINE, AN OXIDATIVELY COUPLED TRIMER OF TYROSINE IN PLANT-CELLWALLS - ITS ROLE IN CROSS-LINK FORMATION

An oxidatively coupled trimer of tyrosine has been isolated from hydro lysates of primary cell walls of a tomato cell culture. UV-absorption, fluorescence and H-1 NMR spectra showed that the trimer was pulcheros ine, composed of isodityrosine and tyrosine oxidatively coupled via a biphenyl linkage such that the aromatic core is 2,2'-dihydroxy-3-pheno xybiphenyl. Pulcherosine could act as an intermediate in the conversio n of isodityrosine to the tetramer, di-isodityrosine. Steric considera tions show that the three tyrosine units of pulcherosine could not be near-neighbour residues within a single polypeptide chain. Pulcherosin e therefore forms inter-polypeptide cross-links and/or wide intra-poly peptide loops. (C) 1997 Elsevier Science Ltd. All rights reserved.