39 高等植物におけるチロシン硫酸化酵素に関する研究

概要

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Protein tyrosine sulfation is an abundant posttranslational modification in mammal cells, and the sulfation reaction is catalyzed by tyrosylprotein sulfotransferase (TPST). Although mammal TPST has been well characterized and human and mouse TPST cDNAs were recently cloned, no information is available about the presence of TPST in higher plants. In 1996, a novel plant growth factor, phytosulfokine (PSK), which is disulfated pentapeptide, has been isolated. This finding appeared to show possibility of the presence of TPST in plant cells. We established an assay system to detect the TPST activity, using synthetic oligopeptides besed on the deduced amino acid sequence of PSK precursor as acceptor substates. TPST activities were found in microsomal membranes of rice, asparagus and carrot cells. We confirmed that acidic amino acid residues adjacent to the tyrosine residues of acceptor peptides were essential to the sulfation reaction, in line with the mammal studies. We investigated the enzymatic properties of TPST; the enzyme exhabited a pH optimum of 7.0-7.5, required manganese ion for the activity and seemed to be membrance bound protein of the Golgi apparatus. This enzyme, is defined as a new class of plant sulfotansferases that may catalyze tyrosine sulfation of PSK and other unknown proteins.
植物化学調節学会の論文
1999-10-01