The estimation of l-phenylalanine ammonia-lyase shows phenylpropanoid biosynthesis to be regulated by l-phenylalanine supply and availability |
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| Institution: | 1. Rheinische Friedrich-Wilhelms-University of Bonn, INRES – Molecular Phytomedicine, Karlrobert-Kreiten-Straße 13, 53115 Bonn, Germany;2. Plant Chemetics Lab, Max-Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany;3. Botanical Institute and Cluster of Excellence on Plant Sciences, University of Cologne, 50674 Cologne, Germany;4. Plant Chemetics Lab, Department of Plant Sciences, University of Oxford, South Parks Road, OX1 3UB Oxford, UK;1. Guangdong Institute of Microbiology, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, State Key Laboratory of Applied Microbiology (Ministry-Guangdong Province Jointly Breeding Base) South China, Guangzhou, China;2. College of Horticulture, South China Agricultural University, Guangzhou, China;3. College of Life Science, Anhui Agricultural University, Hefei, China |
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| Abstract: | l-Phenylalanine ammonia-lyase (PAL, E.C. 4.3.1.5) is the first committed enzyme in the pathway leading to phenylpropanoid biosynthesis in higher plants. PAL catalyses the conversion of l-phenylalanine to t-cinnamic acid with the elimination of ammonia. Standard methods for determination of PAL activity in both green and non-green tissues were found to lead to measurements of both l-phenylalanine amino-transferase (PAT, E.C. 2.6.1.1) and PAL activities together. The accurate estimation of PAL activity alone, necessitated the inhibition of PAT by a specific inhibitor of PAT activity, l-aspartic acid. The influence of PAT on the kinetics of PAL activity may explain (i) the diverse properties that have been attributed to PAL and (ii) the controversies regarding the control mechanism underlying the regulation of PAL activity. Evidence is presented for the regulation of phenylpropanoid biosynthesis via substrate supply and availability as opposed to feedback inhibition, during phaseollin production and hypersensitive necrosis in Phaseolus vulgaris. |
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