Strategy for the Biosynthesis of Short Oligopeptides: Green and Sustainable Chemistry

Biosynthesis, Characterization, and Bioactivity of L-Alanyl-L-tyrosine in Promoting Melanin Synthesis

L-Alanyl-L-tyrosine (L-Ala-Tyr) is a dipeptide formed by the condensation of L-alanine methyl ester and L-tyrosine. After entering the body, it can be rapidly broken down to release tyrosine. In this study, L-Ala-Tyr was successfully prepared by using α-ester acyltransferase as biocatalyst and alanine methyl ester (L-Ala-OMe) and tyrosine (L-Tyr) as acyl donor and nucleophile, respectively. The dipeptide yield was increased from 15 to 50% by optimizing the conditions: boric acid-borax (0.2 mol/L), 30°C, pH 9.5, 2:1 acyl donor to nucleophile ratio, DES (ChCl/urea), and 15%(v/v) water content. The catalytic product is then isolated and purified. The structure of the product was identified by high-performance liquid chromatography, mass spectrometry, proton nuclear magnetic resonance, and carbon spectroscopy. Its biological activity was preliminarily determined by the B16-F10 mouse melanoma cell model. The results showed that the purity of L-Ala-Tyr prepared by the separation and purification method of this study was 96.8%, and the mass spectrometry and nuclear magnetic resonance spectroscopy showed that the structure of the peptide was consistent with the expected structure. In addition, the preliminary physiological activity identification results show that L-Ala-Tyr has no toxic effect on cells in the concentration range of 100-800 μmol·L-1, and at the optimal concentration, compared with the positive control 8-methoxypsoralen, it can promote the production of melanin.

Cyclic Dipeptides: The Biological and Structural Landscape with Special Focus on the Anti-Cancer Proline-Based Scaffold

Cyclic dipeptides, also know as diketopiperazines (DKP), the simplest cyclic forms of peptides widespread in nature, are unsurpassed in their structural and bio-functional diversity. DKPs, especially those containing proline, due to their unique features such as, inter alia, extra-rigid conformation, high resistance to enzyme degradation, increased cell permeability, and expandable ability to bind a diverse of targets with better affinity, have emerged in the last years as biologically pre-validated platforms for the drug discovery. Recent advances have revealed their enormous potential in the development of next-generation theranostics, smart delivery systems, and biomaterials. Here, we present an updated review on the biological and structural profile of these appealing biomolecules, with a particular emphasis on those with anticancer properties, since cancers are the main cause of death all over the world. Additionally, we provide a consideration on supramolecular structuring and synthons, based on the proline-based DKP privileged scaffold, for inspiration in the design of compound libraries in search of ideal ligands, innovative self-assembled nanomaterials, and bio-functional architectures.

Rational engineering of BaLal_16 from a novel Bacillus amyloliquefaciens strain to improve catalytic performance

_L-amino acid ligases (Lals) are promising biocatalysts for the synthesis of dipeptides with special biological properties. However, their poor (or broad) substrate specificity limits their industrial applications. To address this problem, a molecular engineering method for Lals was developed to enhance their catalytic performance. Based on substrate channeling, entrances to the active site for different substrates were identified, and the "gate" located around the active site pocket, which plays an essential role in substrate recognition, was then engineered to facilitate acceptance of _L-Gln. Two mutants (L110Y and N108F/L110Y) were discovered to display significantly increased catalytic activity toward _L-Ala and _L-Gln in the biosynthesis of Ala-Gln. The catalytic efficiency (k_cat/ K_m) of the L110Y and N108F/L110Y mutants was improved by 2.64-fold and 4.06-fold, respectively, compared with that of the wild type. N108F/L110Y was then further applied for batch production of Ala-Gln, which showed that the released Pi yield was 694.47 μM, which was an increase of approximately 21.4 %, and the yield of Ala-Gln was approximately 2.59 mM^-1 L^-1 mg^-1. Collectively, these findings suggest the potential practical application of this method in the rational design of Lals for increased catalytic performance.