Retention of Phenylalanine Ammonia-lyase Activity in Wheat Seedlings during Storage and in Vitro Digestion

Abstract

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.

Silencing a phloretin‐specific glycosyltransferase perturbs both general phenylpropanoid biosynthesis and plant development

“…The negative feedback that exists between PAL and its immediate product, cinnamic acid, has been well documented in a number of species, including tobacco (Blount et al ., ), Triticum (wheat; Lam et al ., ) and Gossypium (cotton; Dubery and Smit, ). PAL inhibition has been shown to operate at both the levels of enzyme activity and transcriptional control (Blount et al ., ), and inhibition can be induced by a number of phenolic compounds, including p ‐coumaric acid, naringenin and quercetin (Sarma and Sharma, ).…”

Biochemical Evaluation of Phenylalanine Ammonia Lyase (PAL) from Endemic Cyathobasis fruticulosa (Bunge) Aellen. for the Dietary Treatment of Phenylketonuria (PKU)

“…Previous reports have indicated a temperature range of 25 to 60 °C for other PAL enzymes derived from Musa sp. (34), Triticum aestivum (19), Ephedra sinica (35) and Vitis vinifera (36). Activities of (39.1±0.1) and (44.6±0.1) U/mg were recorded at 5 and 500 mM buff er concentrations, respectively.…”

“…The enzyme is susceptible to degradation by gastrointestinal proteases when orally administered, necessitating the advancement of novel ways to protect it from enzymatic proteolysis or acidic denaturation and to bring it into contact with enteric Phe (19). Gastric pH has a range between 1.5 and 2, and intestinal pH between 6 and 7.5, depending on dietary factors (37).…”

“…The reaction mixture was incubated with 3 g/L of pepsin (Sigma-Aldrich), pH=2.0 or 4.0, for 30 min at 37 °C to mimic the gastric phase. The reaction mixture was incubated with 1 g/L of pancreatin (Sigma-Aldrich) and 0.30 % bile salt (Difco, Franklin Lakes, NJ, USA), pH=5.5, 7.5 or 9.5, for 30 min at 37 °C to simulate the intestinal phase (19).…”

Discovery and SARs of Trans-3-Aryl Acrylic Acids and Their Analogs as Novel Anti- Tobacco Mosaic Virus (TMV) Agents

“…For example, trans- ferulic acid ( 1 , Figure 1) ubiquitously distributed in primary plant cell walls and crop bran [13] exhibited diverse physiological activities such as reduction of serum cholesterol levels [14], antioxidant properties in several oil models [15], antibacterial [16] and anticancer activity [17], [18]. trans- Cinnamic acid ( 3 , Figure 1) also was found to have allelopathy activity [19], moderate to strong insecticidal activity [20], and a significant inhibitory effect on phenylalanine ammonia-lyase activity in wheat seedlings [21]. Sinapyl acid (Figure 1) possessing the same α, β-unsaturated carbonyl as an important Michael acceptor anticancer pharmacophore displayed potent cytotoxicity against the KB cell line with an IC 50 value of 14 µM [22].…”