Efficient production of γ-aminobutyric acid by glutamate decarboxylase immobilized on an amphiphilic organic-inorganic hybrid porous material.

A novel organic-inorganic hybrid porous material (KCS-2), containing both lipophilic and hydrophilic nanospaces to mimic a lipid bilayer, was utilized as an immobilization support and reaction accelerator for glutamate decarboxylase (GADß). Upon evaluation of the adsorption of GADß on KCS-2, the amount of immobilization was found to be approximately four times higher than that on non-porous silica, and a comparable adsorbability to mesoporous silica was observed. Following γ-aminobutyric acid (GABA) production by the decarboxylation of l-glutamic acid using these immobilized enzymes, the enzymatic activity of the GADß-KCS-2 composite was found to be significantly higher than that of the free enzyme. In contrast, the activity of the more common GADß-mesoporous silica composite decreased. Furthermore, the enzymatic activity of the GADß-KCS-2 composite was superior to those of the un-immobilized free enzyme and the amorphous material itself over a wide temperature range. Thereby, these findings suggest that the amphiphilic nanospace of KCS-2 is suitable as a stable enzyme immobilization field and reaction acceleration field under such conditions. In addition, the durability of the immobilized enzyme was examined in terms of GABA production, with approximately 20% activity retention being observed after 10 cycles using KCS-2. Such durability was not observed for the non-porous silica material due to enzyme desorption.

Enzyme Immobilization in Mesoporous Silica for Enhancement of Thermostability.

Direct enzyme immobilization by encapsulation in the pores of mesoporous silica particles enhances protein thermal and chemical stability. In this study, we investigated the effect of pore size on the thermostability and catalytic activity of Escherichia coli glutaminase YbaS encapsulated under high temperature conditions in two SBA-type mesoporous silicas: SBA5.4 and SBA10.6 with pore diameters of 5.4 and 10.6 nm, respectively. The changes in enzyme conformation under high temperature conditions were assessed using PSA, a benzophenoxazine-based fluorescent dye that is sensitive to denatured aggregated proteins. The results showed that YbaS adsorption to SBA10.6 was higher than that to SBA5.4 and that SBA10.6-encapsulated YbaS was more resistant to heat treatment and maintained higher conformational stability than SBA5.4-encapsulated or free enzyme. Moreover, the heat-treated YbaS-SBA10.6 composite demonstrated high catalytic activity in glutamine hydrolysis. Thus, enzyme encapsulation in suitable silica mesopores can prevent heat-induced denaturation and subsequent aggregation of the enzyme.

Three-Component, Diastereoselective Prins-Ritter Reaction for cis-Fused 4-Amidotetrahydropyrans toward a Precursor for Possible Neuronal Receptor Ligands.

Here, we report an unprecedented, highly diastereoselective Prins-Ritter reaction of aldehydes, homoallylic alcohols, and nitriles in a three-component coupling reaction for the synthesis of tetra-cis-substituted 4-amidotetrahydropyrans. In this study, the reaction was not only applied for carbohydrate-based heterobicycles but also for more complex heterotricycles, showing acceptable levels of conversion yield (42-97% BRSM) and exclusive diastereoselectivity. Furthermore, the latter heterotricycles were converted to nine analogues of our neuronal receptor ligands IKM-159 and MC-27. An in vivo assay by intracerebroventricular injection in mice suggested that the substituent at C9 of the novel analogues interferes with the molecular interactions with the AMPA receptor, which was originally observed in the complex of IKM-159 and the GluA2 ligand binding domain. Our research has thus shown the power of a multicomponent coupling reaction for the preparation of a structurally diverse compound collection to study structure-activity relationships of biologically active small molecules.

Structure-activity relationships of IKM-159: Diverted synthesis and biological evaluation of a series of C5-oxy analogs.

Ligands for neuronal receptors are important for understanding the biological functions as well as for treatment of neuronal diseases associated with. Here, we report diverted synthesis and biological evaluation of four C-ring analogs of IKM-159, a subtype-selective inhibitor for (S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA)-type ionotropic glutamate receptor. Starting from iodinated 7-oxanorbornene 7, those analogs 3-6 were successfully synthesized in 7.0-33% yields over 8-11 steps via a common intermediate 13. Intracerebroventricular injection of those analogs on mice showed that introduction of oxo group on the C-ring (analogs 4, 5) or cleavage of the C-ring (analog 6) caused significant loss of the activity, while the ether analog 3 still retain the suppressed motor activity, indicating the importance of the C-ring in the neuronal activity of IKM-159.