Biosynthesis of 4-hydroxyphenylpyruvic acid from l-tyrosine using recombinant Escherichia coli cells expressing membrane bound l-amino acid deaminase

Ionic titanium is expected to improve the nutritional quality of Tartary buckwheat sprouts through flavonoids and amino acid metabolism

Tartary buckwheat sprouts are highly valued by consumers for their superior nutritional content. Ionic titanium (Ti) has been shown to enhance crop growth and improve nutritional quality. However, there is limited research on the impact of ionic Ti on the nutritional quality of Tartary buckwheat sprouts. This study cultivated Tartary buckwheat sprouts with ionic Ti and found that the high concentration of ionic Ti significantly increased the contents of chlorophyll a, chlorophyll b, and carotenoids (increased by 25.5%, 27.57%, and 15.11%, respectively). The lower concentration of ionic Ti has a higher accumulation of total flavonoids and total polyphenols. Metabolomics analysis by LC-MS revealed 589 differentially expressed metabolites and 54 significantly different metabolites, enriching 82 metabolic pathways, especially including amino acid biosynthesis and flavonoid biosynthesis. This study shows that ionic Ti can promote the growth of Tartary buckwheat sprouts, improve nutritional quality, and have huge development potential in food production.

Biosynthesis of α-keto acids and resolution of chiral amino acids by l-amino acid deaminases from Proteus mirabilis

Chiral amino acids and their deamination products, α-keto acids, have important applications in food, medicine, and fine chemicals. In this study, two l-amino acid deaminase genes from Proteus mirabilis, PM473 of type Ⅰ and PM471 of type Ⅱ were cloned and expressed in Escherichia coli respectively, expected to achieve the chiral separation of amino acids. Extensive substrate preference testing showed that both deaminases had catalytic effects on the d-amino acid component of the D, l-amino acids, and PM473 has a wider catalytic range for amino acids. When D, L-Cys was used as the substrate, all L-Cys components and 75.1 % of D-Cys were converted to mercapto pyruvate, and the remaining D-Cys was a single chiral enantiomer. Molecular docking analysis showed that the interaction between the substrate and the key residues affected the stereoselectivity of enzymes. The compatibility of hydrophobicity between the binding pocket and substrate may be the basic factor that affects the substrate selectivity. This work provides an alternative method for the production of α-keto acids and the resolution of chiral amino acids.

Production of Salvianic Acid A from l-DOPA via Biocatalytic Cascade Reactions

Salvianic acid A (SAA), as the main bioactive component of the traditional Chinese herb Salvia miltiorrhiza, has important application value in the treatment of cardiovascular diseases. In this study, a two-step bioprocess for the preparation of SAA from l-DOPA was developed. In the first step, l-DOPA was transformed to 3,4-dihydroxyphenylalanine (DHPPA) using engineered Escherichia coli cells expressing membrane-bound L-amino acid deaminase from Proteus vulgaris. After that, the unpurified DHPPA was directly converted into SAA by permeabilized recombinant E. coli cells co-expressing d-lactate dehydrogenase from Pediococcus acidilactici and formate dehydrogenase from Mycobacterium vaccae N10. Under optimized conditions, 48.3 mM of SAA could be prepared from 50 mM of l-DOPA, with a yield of 96.6%. Therefore, the bioprocess developed here was not only environmentally friendly, but also exhibited excellent production efficiency and, thus, is promising for industrial SAA production.

Blood and Urinary Biomarkers of Antipsychotic-Induced Metabolic Syndrome

Metabolic syndrome (MetS) is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Antipsychotic (AP)-induced MetS (AIMetS) is the most common adverse drug reaction (ADR) of psychiatric pharmacotherapy. Herein, we review the results of studies of blood (serum and plasma) and urinary biomarkers as predictors of AIMetS in patients with schizophrenia (Sch). We reviewed 1440 studies examining 38 blood and 19 urinary metabolic biomarkers, including urinary indicators involved in the development of AIMetS. Among the results, only positive associations were revealed. However, at present, it should be recognized that there is no consensus on the role of any particular urinary biomarker of AIMetS. Evaluation of urinary biomarkers of the development of MetS and AIMetS, as one of the most common concomitant pathological conditions in the treatment of patients with psychiatric disorders, may provide a key to the development of strategies for personalized prevention and treatment of the condition, which is considered a complication of AP therapy for Sch in clinical practice.

Semi-Rational Design of Proteus mirabilis l-Amino Acid Deaminase for Expanding Its Substrate Specificity in α-Keto Acid Synthesis from l-Amino Acids

l-amino acid deaminases (LAADs) are flavoenzymes that catalyze the stereospecific oxidative deamination of l-amino acids into α-keto acids, which are widely used in the pharmaceutical, food, chemical, and cosmetic industries. However, the substrate specificity of available LAADs is limited, and most substrates are concentrated on several bulky or basic l-amino acids. In this study, we employed a LAAD from Proteus mirabilis (PmiLAAD) and broadened its substrate specificity using a semi-rational design strategy. Molecular docking and alanine scanning identified F96, Q278, and E417 as key residues around the substrate-binding pocket of PmiLAAD. Site-directed saturation mutagenesis identified E417 as the key site for substrate specificity expansion. Expansion of the substrate channel with mutations of E417 (E417L, E417A) improved activity toward the bulky substrate l-Trp, and mutation of E417 to basic amino acids (E417K, E417H, E417R) enhanced the universal activity toward various l-amino acid substrates. The variant PmiLAADE417K showed remarkable catalytic activity improvement on seven substrates (l-Ala, l-Asp, l-Ile, l-Leu, l-Phe, l-Trp, and l-Val). The catalytic efficiency improvement obtained by E417 mutation may be attributed to the expansion of the entrance channel and its electrostatic interactions. These PmiLAAD variants with a broadened substrate spectrum can extend the application potential of LAADs.

Recent advances in biocatalytic derivatization of L-tyrosine

L-Tyrosine is an aromatic, polar, non-essential amino acid that contains a highly reactive α-amino, α-carboxyl, and phenolic hydroxyl group. Derivatization of these functional groups can produce chemicals, such as L-3,4-dihydroxyphenylalanine, tyramine, 4-hydroxyphenylpyruvic acid, and benzylisoquinoline alkaloids, which are widely employed in the pharmaceutical, food, and cosmetics industries. In this review, we summarize typical L-tyrosine derivatizations catalyzed by enzymatic biocatalysts, as well as the strategies and challenges associated with their production processes. Finally, we discuss future perspectives pertaining to the enzymatic production of L-tyrosine derivatives.Key points• Summary of recent advances in enzyme-catalyzed L-tyrosine derivatization.• Highlights of relevant strategies involved in L-tyrosine derivatives biosynthesis.• Future perspectives on industrial applications of L-tyrosine derivatization.

Engineering of L-amino acid deaminases for the production of α-keto acids from L-amino acids

α-keto acids are organic compounds that contain an acid group and a ketone group. L-amino acid deaminases are enzymes that catalyze the oxidative deamination of amino acids for the formation of their corresponding α-keto acids and ammonia. α-keto acids are synthesized industrially via chemical processes that are costly and use harsh chemicals. The use of the directed evolution technique, followed by the screening and selection of desirable variants, to evolve enzymes has proven to be an effective way to engineer enzymes with improved performance. This review presents recent studies in which the directed evolution technique was used to evolve enzymes, with an emphasis on L-amino acid deaminases for the whole-cell biocatalysts production of α-keto acids from their corresponding L-amino acids. We discuss and highlight recent cases where the engineered L-amino acid deaminases resulted in an improved production yield of phenylpyruvic acid, α-ketoisocaproate, α-ketoisovaleric acid, α-ketoglutaric acid, α-keto-γ-methylthiobutyric acid, and pyruvate.

An efficient biocatalytic synthesis of imidazole-4-acetic acid

OBJECTIVE

To develop a new and efficient biocatalytic synthesis method of imidazole-4-acetic acid (IAA) from L-histidine (L-His).

RESULTS

L-His was converted to imidazole-4-pyruvic acid (IPA) by an Escherichia coli whole-cell biocatalyst expressing membrane-bound L-amino acid deaminase (mL-AAD) from Proteus vulgaris firstly. The obtained IPA was subsequently decarboxylated to IAA under the action of H₂O₂. Under optimum conditions, 34.97 mM IAA can be produced from 50 mM L-His, with a yield of 69.9%.

CONCLUSIONS

Compared to the traditional chemical synthesis, this biocatalytic method for IAA production is not only environmentally friendly, but also more cost effective, thus being promising for industrial IAA production.