Novel amidases of two Aminobacter sp. strains: Biotransformation experiments and elucidation of gene sequences

Synthesis and interest in medicinal chemistry of β-phenylalanine derivatives (β-PAD): an update (2010-2022)

β-Phenylalanine derivatives (β-PAD) represent a structural family of therapeutic interest, either as components of drugs or as starting materials for access to key compounds. As scaffolds for medicinal chemistry work, β-PAD offer the advantage of great diversity and modularity, a chiral pseudopeptidic character that opens up the capacity to be recognized by natural systems, and greater stability than natural α-amino acids. Nevertheless, their synthesis remains a challenge in drug discovery and numerous methods have been devoted to their preparation. This review is an update of the access routes to β-PAD and their various therapeutic applications.

Comparative genomic analysis of iprodione-degrading Paenarthrobacter strains reveals the iprodione catabolic molecular mechanism in Paenarthrobacter sp. strain YJN-5

Degradation of the fungicide iprodione by the Paenarthrobacter sp. strain YJN-5 is initiated via hydrolysis of its N1 amide bond to form N-(3,5-dichlorophenyl)-2,4-dioxoimidazolidine. In this study, another iprodione-degrading strain, Paenarthrobacter sp. YJN-D, which harbours the same metabolic pathway as strain YJN-5 was isolated and characterized. The genes that encode the conserved iprodione catabolic pathway were identified based on comparative analysis of the genomes of the two iprodione-degrading Paenarthrobacter sp. and subsequent experimental validation. These genes include an amidase gene, ipaH (previously reported in AEM e01150-18); a deacetylase gene, ddaH, which is responsible for hydantoin ring cleavage of N-(3,5-dichlorophenyl)-2,4-dioxoimidazolidine, and a hydrolase gene, duaH, which is responsible for cleavage of the urea side chain of (3,5-dichlorophenylurea)acetic acid, thus yielding 3,5-dichloroaniline as the end product. These iprodione-catabolic genes are distributed on three plasmids in strain YJN-5 and are highly conserved between the two iprodione-degrading Paenarthrobacter strains. However, only the ipaH gene is flanked by a mobile genetic element. Two iprodione degradation cassettes bearing ipaH-ddaH-duaH were constructed and expressed in strains Pseudomonas putida KT2440 and Bacillus subtilis SCK6 respectively. Our findings enhance the current understanding of the microbial degradation mechanism of iprodione.

Chemical synthesis and enzymatic, stereoselective hydrolysis of a functionalized dihydropyrimidine for the synthesis of β-amino acids

A novel substrate, 6-(4-nitrophenyl)dihydropyrimidine-2,4(1H,3H)-dione (pNO₂PheDU), was chemically synthesized and analytically verified for the potential biocatalytic synthesis of enantiopure β-amino acids. The hydantoinase (EC 3.5.2.2) from Arthrobacter crystallopoietes DSM20117 was chosen to prove the enzymatic hydrolysis of this substrate, since previous investigations showed activities of this enzyme toward 6-monosubstituted dihydrouracils. Whole cell biotransformations with recombinant Escherichia coli expressing the hydantoinase showed degradation of pNO₂PheDU. Additionally, the corresponding N-carbamoyl-β-amino acid (NCarbpNO₂βPhe) was chemically synthesized, an HPLC-method with chiral stationary phases for detection of this product was established and thus (S)-enantioselectivity toward pNO₂PheDU has been shown. Consequently this novel substrate is a potential precursor for the enantiopure β-amino acid para-nitro-β-phenylalanine (pNO₂βPhe).

Process parameter optimization for hydantoinase-mediated synthesis of optically pure carbamoyl amino acids of industrial value using Pseudomonas aeruginosa resting cells

Hydantoinase-mediated enzymatic synthesis of optically pure carbamoyl amino acids was investigated as an environmentally friendly, energy-efficient alternative to the otherwise energy-intensive, polluting chemical synthesis. Hydantoinase-producing bacterial strain was identified as Pseudomonas aeruginosa by 16S rRNA gene sequencing and biochemical profiling using the BIOLOG Microbial Identification System. Hydantoinase activity was assessed using hydantoin analogs and 5-monosubstituted hydantoins as substrates in a colorimetric assay. The hydantoinase gene was PCR amplified using gene-specific primers and sequenced on an automated gene analyzer. Hydantoinase gene sequence of P. aeruginosa MCM B-887 revealed maximum homology of only 87 % with proven hydantoinase gene sequences in GenBank. MCM B-887 resting cells converted >99 % of substrate into N-carbamoyl amino acids under optimized condition at 42 °C, pH 8.0, and 100 mM substrate concentration in <120 min. Hydantoin hydrolyzing activity was D-selective and included broad substrate profile of 5-methyl hydantoin, 5-phenyl hydantoin, 5-hydroxyphenyl hydantoin, o-chlorophenyl hydantoin, as well as hydantoin analogs such as allantoin, dihydrouracil, etc. MCM B-887 resting cells may thus be suitable for bio-transformations leading to the synthesis of optically pure, unnatural carbamoyl amino acids of industrial importance.