1.Enzymatic dynamic kinetic resolution of racemic N-formyl- and N-carbamoyl-amino acids using immobilized L-N-carbamoylase and N-succinyl-amino acid racemase.
Soriano-Maldonado P1, Las Heras-Vazquez FJ, Clemente-Jimenez JM, Rodriguez-Vico F, Martínez-Rodríguez S. Appl Microbiol Biotechnol. 2015 Jan;99(1):283-91. doi: 10.1007/s00253-014-5880-7. Epub 2014 Jul 4.
Taking advantage of the catalytic promiscuity of L-carbamoylase from Geobacillus stearothermophilus CECT43 (BsLcar) and N-succinyl-amino acid racemase from Geobacillus kaustophilus CECT4264 (GkNSAAR), we have evaluated the production of different optically pure L-α-amino acids starting from different racemic N-formyl- and N-carbamoyl-amino acids using a dynamic kinetic resolution approach. The enzymes were immobilized on two different solid supports, resulting in improved stability of the enzymes in terms of thermostability and storage when compared to the enzymes in solution. The bienzymatic system retained up to 80% conversion efficiency after 20 weeks at 4 °C and up to 90% after 1 week at 45 °C. The immobilization process also resulted in a great enhancement of the activity of BsLcar toward N-formyl-tryptophan, showing for the first time that substrate specificity of L-carbamoylases can be influenced by this approach. The system was effective for the biosynthesis of natural and unnatural L-amino acids (enantiomeric excess (e.
2.Enhancement of biocatalytic efficiency by increasing substrate loading: enzymatic preparation of L-homophenylalanine.
Zhang J1, Zhu T, Wu X, Chen Y. Appl Microbiol Biotechnol. 2013 Oct;97(19):8487-94. doi: 10.1007/s00253-013-5117-1. Epub 2013 Jul 28.
Enantiomerically pure L-homophenylalanine (L-HPA) is a key building block for the synthesis of angiotensin-converting enzyme inhibitors and other chiral pharmaceuticals. Among the processes developed for the L-HPA production, biocatalytic synthesis employing phenylalanine dehydrogenase has been proven as the most promising route. However, similar to other dehydrogenase-catalyzed reactions, the viability of this process is markedly affected by insufficient substrate loading and high costs of the indispensable cofactors. In the present work, a highly efficient and economic biocatalytic process for L-HPA was established by coupling genetically modified phenylalanine dehydrogenase and formate dehydrogenase. Combination of fed-batch substrate addition and a continuous product removal greatly increased substrate loading and cofactor utilization. After systemic optimization, 40 g (0.22 mol) of keto acid substrate was transformed to L-HPA within 24 h and a total of 0.
3.Formation of Benzyl Carbanion in Collision-Induced Dissociation of Deprotonated Phenylalanine Homologues.
Sekimoto K1, Matsuda N1, Takayama M1. Mass Spectrom (Tokyo). 2014;3(1):A0027. doi: 10.5702/massspectrometry.A0027. Epub 2014 May 29.
The fragmentation behavior of deprotonated L-phenylalanine (Phe) and its homologues including L-homophenylalanine (HPA) and L-phenylglycine (PG) was investigated using collision-induced dissociation mass spectrometry coupled with a negative ion atmospheric pressure corona discharge ionization (APCDI) technique. The deprotonated molecules [M-H](-) fragmented to lose unique neutral species, e.g., the loss of NH3, CO2, toluene and iminoglycine for [Phe-H](-); styrene and ethenamine/CO2 for [HPA-H](-); and CO2 for [PG-H](-). All of the fragmentations observed are attributable to the formation of intermediates and/or product ions which include benzyl carbanions having resonance-stabilized structures. The carbanions are formed via proton rearrangement through a transition state or via a simple dissociation reaction. These results suggest that the principal factor governing the fragmentation behavior of deprotonated Phe homologues is the stability of the intermediate and/or product ion structures.
4.Strong and fast-recovery organic/inorganic hybrid AuNPs-supramolecular gels based on loofah-like 3D networks.
He H1, Chen S, Tong X, Chen Y, Wu B, Ma M, Wang X, Wang X. Soft Matter. 2016 Jan 21;12(3):957-64. doi: 10.1039/c5sm02269j. Epub 2015 Nov 16.
Super strong and fast-recovery organic/inorganic hybrid gold nanoparticle (AuNPs)-supramolecular gels based on a three-dimensional loofah-like nanoscale network self-assembled by polyhedral oligomeric silsesquioxane (POSS) core supramolecular gelators are reported for the first time. Two series of POSS core organic/inorganic hybrid gelators, POSS-BOC-l-Homophenylalanine (POSS-Hpy) and POSS-Boc-Cys(Bzl)-OH (POSS-Cys), with two types of peripherals having different abilities for driving the self-assembly of AuNPs in gels were designed and synthesized, both of which self-assembled into three-dimensional loofah-like nanoscale gel networks producing hybrid physical gels with fast-recovery behaviors. The mechanical properties of the resultant hybrid gels were dramatically increased by as much as 100 times in the system of sulfur containing POSS-Cys gelators without destroying the fast-recovery behaviors, with the addition of AuNPs, which had direct interaction with AuNPs to give S-Au non-covalent driving force to lead AuNPs self-assemble onto the 3D loofah-like network nanofibres in the supramolecular hybrid gel system.
