Screening of phenylalanine ammonia lyase in plant tissues, and retention of activity during dehydration

Abstract

BACKGROUND: Oral therapy with phenylalanine ammonia lyase (PAL), naturally encapsulated in plant cells, may provide a potential alternative treatment for hyperphenylalaninemic patients, including those with phenylketonuria. Therefore different sources of plant tissue were investigated for PAL activity. RESULTS: Enzyme activity was highest in grain seedlings, with maximal enzyme activity in 7-day-old red spring wheat (Triticum aestivum L.) seedlings. The PAL activities of leaves and roots/endosperm of wheat seedlings were 11.90 ± 2.64 and 6.48 ± 1.59 μmol h-1 g-1 dry weight respectively. Three PAL-related polypeptides with molecular weights of 74, 83 and 103 kDa were identified in wheat seedling leaf tissues, while only the 74kDa polypeptide was detected in root/endosperm tissues. Dehydration was investigated as a method of concentrating PAL in wheat seedlings. Freeze-drying was found to retain the most PAL activity (>90% recovery on a dry weight basis) compared with air drying and vacuum microwave drying for both leaf and root/endosperm samples. CONCLUSION: This study has led to a better understanding of PAL activity and stability in plant tissues and provides the basis for developing a natural plant preparation as a dietary supplement for the treatment of hyperphenylalaninemia. © 2007 Society of Chemical Industry.