Metabolism of aromatic amino acids in glyoxysomes

Article abstract of DOI:10.1016/S0031-9422(00)97255-8

Investigations were carried out on the possible role of glyoxysomes from the endosperm of Ricinus communis in the metabolism of aromatic amino acids. l-Phenylalanine was shown to be mainly converted to cinnamic acid by isolated glyoxysomes. Smaller amounts of p-coumaric acid and benzoic acid were also detected. p-Coumaric acid is formed by hydroxylation from cinnamic acid more actively in proplastids and microsomes than in glyoxysomes. p-Coumaric acid was the main product of metabolism of l-tyrosine. A remarkably large amount of p-hydroxybenzoic acid was also found indicating a chain shortening process, which in vivo has been shown before to be responsible for the formation of hydroxybenzoic acids in higher plants. Formation of p-hydroxyphenylacetic acid and homogentisic acid was also detected. The results demonstrate the capability of glyoxysomes to metabolize aromatic amino acids. This finding adds an entirely new aspect to the knowledge on metabolism in glyoxysomes. Proplastids from the same tissue show a different pattern of products.