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Plant and Cell Physiology, 1974, Vol. 15, No. 3 429-440
© 1974

Article

Purification and some properties of L-tyrosine carboxy-lyase from barley roots

Kazuo Hosoi

Department of Biology, Faculty of Science, Tokyo Metropolitan University Fukazawa, Setagaya-ku, Tokyo 158, Japan

L-Tyrosine carboxy-lyase (E. C. 4. 1. 1. 25) was extracted from the roots of barley seedlings and purified approximately 25 fold. Optimum pH for the enzyme activity was found to be 7.3. The Km value for L-tyrosine was calulated as 4.5×10–4M. D-Isomer did not react with the enzyme. L-DOPA, m-tyrosine and o-tyrosine were decarboxylated to some extent. Pyridoxal phosphate activated the enzyme 4 fold. Caffeic acid and p-coumaric acid are competitive inhibitors. Ki values were 4.5×10–5M for caffeic acid and 1.6×10–4M for p-coumaric acid. L-DOPA and m-tyrosine had an inhibitory effect on the decarboxylation of L-tyrosine. Hydroxylamine, semicarbazide, p-CMB, Fe++, Cu++, and Hg++ inhibited the decarboxylation of tyrosine. Enzyme activity was also found in extracts from Triticum aestivum, Zea mays and Cytisus scoparius.

(Received November 30, 1973; )
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