Lam M, Scaman C H, Clemens S, Kermode A
University of British Columbia, Vancouver, Canada.
J Agric Food Chem. 2008 Dec 10;56(23):11407-12. doi: 10.1021/jf8021942.
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.
为评估植物苯丙氨酸解氨酶（PAL）作为患有代谢疾病苯丙酮尿症患者膳食补充剂的功效，对红春小麦幼苗在储存期间及体外蛋白质消化过程中PAL活性的保留情况进行了评估。在-20℃储存三个月后，冻干小麦幼苗组织中PAL活性的保留率在叶片中为62%，在根/残留种子组织中为89%。经过3小时的两阶段（“胃-肠”）体外消化后，切碎的新鲜叶片和根/残留种子组织中PAL活性的回收率分别为36%和42%；然而，冻干组织中未检测到活性。体外消化后对残留苯丙氨酸（Phe）的高效液相色谱分析证实，新鲜组织对外源Phe的转化率明显高于冻干组织。这些结果表明，植物细胞壁在体外消化过程中对PAL起到了保护作用。在外源Phe（100mg；24mM）供应给组织的情况下，反应产物反式肉桂酸可能对PAL活性产生了显著抑制作用。
