Retention of phenylalanine ammonia-lyase activity in wheat seedlings during storage and in vitro digestion.
The retention of phenylalanine ammonia-lyase (PAL) activity in Red Spring wheat seedlings during storage and in vitro protein digestion was evaluated toward assessing the efficacy of plant PAL as a dietary supplement for patients suffering from the metabolic disease, phenylketonuria. Retention of PAL activity in freeze-dried wheat seedling tissues following three months of storage at -20 degrees C ranged from 62% in the leaf to 89% in root/residual seed tissues. After a 3-h two-stage ("gastric-intestinal") in vitro digestion, 36% and 42% recovery of PAL activity was associated with chopped fresh leaf and root/residual seed tissues respectively; however, no activity was recovered from freeze-dried tissues. High performance liquid chromatographic analysis of the residual phenylalanine (Phe) after in vitro digestion confirmed that the fresh tissues effected a significantly higher conversion of exogenous Phe than freeze-dried tissues. These results demonstrate that the plant cell walls provide protection of PAL during in vitro digestion. In cases where exogenous Phe (100 mg; 24 mM) was supplied to the tissues, the product of the reaction, trans-cinnamic acid, may have exerted a significant inhibitory effect on PAL activity.
Lam
M
M
University of British Columbia, Vancouver, Canada.
Scaman
C H
CH
Clemens
S
S
Kermode
A
A
D004063:Digestion; D004795:Enzyme Stability; D005511:Food Handling; D005612:Freeze Drying; D005744:Gastric Acid; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D010649:Phenylalanine / Q000378:metabolism; D010650:Phenylalanine Ammonia-Lyase / Q000737:chemistry* / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D036226:Seedlings / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D014908:Triticum / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism
D010940:Plant Proteins; D010649:Phenylalanine; D010650:Phenylalanine Ammonia-Lyase