PLP-dependent enzymes described on this review are attractive targets for enzyme engineering towards their application in an industrial biotechnology framework.

Many fungal quinazolinone metabolites, which contain the methyl-indole pyrazino [1,2-b]quinazoline-3,6-dione core, have been found to possess promising antitumor activity. The purpose of this work was to synthesize the enantiomeric pairs of two members of this quinazolinone family, to explore their potential as antitumor and their ability to revert multidrug resistance. The marine natural product fiscalin B (4c), and antienantiomers (4b, 5b, and 5c) were synthesized via a one-pot approach, while the syn enantiomers (4a, 4d, 5a, and 5d) were synthetized by a multi-step procedure. These strategies used anthranilic acid (i), chiral N-protected α-amino acids (ii), and tryptophan methyl esters (iii) to form the core ring of pyrazino[2,1-b]quinazoline-3,6-dione scaffold. Four enantiomeric pairs, with different enantiomeric purities, were obtained with overall yields ranging from 7 to 40%. Compounds 4a–d and 5a–d were evaluated for their growth inhibitory effect against two tumor cell lines. Differences between enantiomeric pairs were noted and 5a–d displayed GI₅₀ values ranging from 31 to 52 μM, which are lower than those of 4a–d. Nevertheless, no effect on P-glycoprotein (P-gp) modulation was observed for all compounds. This study disclosed new data for fiscalin B (4c), as well as for its analogues for a future development of novel anticancer drug leads.

Increased levels of cathepsin B (CatB), a cysteine protease, have been associated with different types of tumors, including prostate cancer. Hence, the identification of novel targeting ligands homing CatB may be a promising approach for the development of CatB-targeted therapies. In this work, a methodology called systematic evolution of ligands by EXponential enrichment (SELEX) was used to generate and isolate new aptamers targeting CatB. After 8 rounds of selection, the pool was sequenced, and the 10 most prevalent sequences, along with their corresponding reverse complementary sequences, were further analyzed. In order to assess the binding affinity of the aptamers towards the CatB, bioinformatics tools were used. After generating the 3D structures for each aptamer, the HADDOCK software was used for the docking studies between them and CatB. Molecular dynamics simulations and free binding energy calculations by molecular mechanics-generalized born surface area (MM-GBSA) allowed selection of a new aptamer with potential to target CatB. Cell binding assays against the PC-3 prostate cancer cell line confirmed the in silico predictions, further validating the newly discovered aptamer as a promising targeting ligand for CatB-overexpressing cancer cells.

An atomistic description of Pdx2 catalytic mechanism is provided by QM/MM methodologies. Pdx2, the glutaminase subunit of pyridoxal 5’-phosphate (PLP) synthase, is characterized by a Cys-His-Glu catalytic triad used to deaminate glutamine to glutamate. While being absent in humans, Pdx2 is essential for the development and replication of the protozoan Plasmodium falciparum and Mycobacterium tuberculosis pathogens, which are responsible for two deadly diseases, malaria and tuberculosis, respectively. Pdx2 is thus a promising drug target for fighting these diseases. More information can be found in the Full Paper by A. F. Pina et al.