Preformulation studies with phenylalanine ammonia lyase: essential prelude to a microcapsule formulation for the management of phenylketonuria

Metabolomics unravels the formation pathway of advanced glycation end products in preserved egg yolk mediated by OH- during pickling

Metabolomics was first applied to explore the formation pathway and regulatory factors for advanced glycation end products (AGEs) in preserved egg yolk (PEY) during pickling. Most reactions that contributed to formation of AGEs, including oxidation and/or degradation of matrix/precursors and Maillard reaction, occurred primarily in PEY in early stage, and lipid oxidation occurred prior to protein oxidation. Additionally, the formation of Nε-carboxymethyl-lysine (CML) in PEY was mainly attributed to glyoxal derived from D-glucuronic acid in early stage based on the correlation between metabolites and AGEs. Reactive oxygen radicals from oxidized lipids also promoted the enrichment of CML and Nε-carboxymethyl-lysine (CEL). Moreover, during later stage, the accumulation of CEL was enhanced through methylglyoxal from Schiff bases, and acidic compounds could inhibit AGEs via hindering Maillard reaction. This manuscript pioneered the application of metabolomics to reveal the formation pathway of AGEs, and will provide new perspective on AGEs formation in foods.

Agricultural wastes: a new promising source for phenylalanine ammonia-lyase as anticancer agent

The present study aims to investigate the physicochemical characteristics of phenylalanine ammonia-lyase (PAL) extracted from agricultural waste and its potential use as an anticancer agent in comparison to microbial PAL. We extracted and partially purified PAL from agricultural waste sources. We assessed the temperature and pH range of PAL and determined enzyme kinetics parameters including Michaelis constants (Km), maximum velocity (Vmax), and specificity constant values (Vmax/Km). Additionally, we examined the effects of different storage temperatures on PAL activity. In our analysis, we compared the efficacy of agricultural waste-derived PAL with PAL from Rhodotorula glutinis. The results demonstrated that PAL extracted from agricultural waste exhibited significantly higher specific activity (Vmax/Km) compared to its microbial counterpart. The agricultural waste-derived PAL displayed a stronger affinity for phenylalanine, as indicated by a lower Km value than the microbial PAL did. Furthermore, PAL from agricultural waste maintained activity across a broader temperature and pH range (15-75 °C, pH 5-11), in contrast to microbial PAL (20-60 °C, pH 5.5-10). Importantly, the PAL derived from agricultural waste exhibited superior stability, retaining over 90% of its activity after 6 months of storage at room temperature (25 °C), whereas microbial PAL lost more than 70% of its activity under similar storage conditions. In anticancer experiments against various cancer cell lines, agricultural waste-derived PAL demonstrated greater anticancer activity compared to microbial PAL. These findings suggest that PAL sourced from agricultural waste has the potential to be a safe and effective natural anticancer agent.

Pharmacodynamics, safety, tolerability and pharmacokinetics of a single oral dose of an engineered phenylalanine ammonia-lyase in patients with phenylketonuria

The cornerstone treatment of hyperphenylalaninemia (HPA) and phenylketonuria (PKU) is a lifelong low-protein diet with phenylalanine (Phe) free L-amino acid supplements. However, the PKU diet has significant shortcomings, and there is a clinically unmet need for new therapeutics to improve patient outcomes. CDX-6114 is a modified phenylalanine ammonia-lyase (PAL) enzyme obtained by a mutation in the Anabaena variabilis PAL sequence. CodeEvolver® protein engineering technology has been applied to improve the degradation resistance of the enzyme. In our first phase I trial, 19 patients were given a single oral dose of CDX-6114 at 7.5 g, 2.5 g, 0.7 g, or placebo in a cross-over design. After an overnight fast, patients received a standardised breakfast of 20 g of protein, thus exceeding the dietary recommendations for a single meal in patients with PKU. Plasma levels of Phe and cinnamic acid (CA) were measured over a 5-h period following CDX-6114 dosing. During the development of CDX-6114, a stability assessment using reverse-phase high-performance liquid chromatography (HPLC) assay revealed two peaks. The second peak was identified as CA. It was not previously known that as part of the mechanism of action, the CA remained associated with the protein following the conversion of Phe. Thus, recalculating the historical PAL enzyme amounts in CDX-6114 bulk substance was necessary. An updated extinction coefficient was achieved by applying a correction factor of 0.771 to previously reported doses. Postprandial plasma levels of Phe increased in all dose cohorts over time between 10% and 30% from baseline, although the actual peak of Phe levels was not achieved within the 5-h observation. When accounting for the interquartile ranges, these concentrations were similar to the placebo. As plasma levels of Phe were no longer a reliable marker for pharmacodynamics, the consistently detectable amount of CA seen in all patients who received CDX-6114 provided proof of the enzymatic activity of CDX-6114 in metabolising gastrointestinal Phe. Peak levels of CA were seen shortly after CDX-6114 intake, with a rapid decline, and remained low compared with the plasma Phe levels. This pattern indicates a short half-life, possibly due to the liquid formulation or the inability to withstand the lower pH in the human stomach compared with animal models in earlier studies. This was the first trial in patients with PKU to establish the safety and tolerability of CDX-6114. A single dose of CDX-6114 was safe and well tolerated, with no serious adverse events or presence of anti-drug antibodies detected. Efficacy will be explored in future trials using an optimised formulation.