Priyanka Bajaj

Chiral amines are critical intermediates in pharmaceutical synthesis, with transaminases serving as efficient biocatalysts for their production. CDX-036, a well-characterized engineered transaminase, is widely used in the industrial synthesis of sitagliptin. However, high operational costs necessitate enzyme recyclability to enhance process economics. In this study, CDX-036 was immobilized onto dextrin aldehyde, a cost-effective and abundantly available support, to create a stable and reusable biocatalyst. Dextrin was oxidized using sodium periodate to yield dextrin aldehyde, confirmed by DNPH assay, FTIR, NMR, and SEM. The enzyme was immobilized via Schiff base formation with an optimal loading yield of 82% at a 1:5 enzyme-to-support ratio. Immobilized CDX-036 exhibited superior catalytic efficiency, achieving up to 92% conversion of pro-sitagliptin to sitagliptin in the first cycle—compared to up to 80% with the free enzyme. Notably, the immobilized enzyme retained high activity over five cycles, demonstrating excellent stability and reusability. Characterization by SEM, FTIR, and NMR confirmed successful immobilization. This method presents a scalable, economical, and industrially relevant strategy for enzyme reuse without compromising performance. To our knowledge, this is the first report detailing a robust immobilization strategy for CDX-036, directly applicable to sitagliptin synthesis at commercial scale.

Enzymes have been used for disease diagnosis for many decades; however, advancements in technology like ELISA and flow cytometry-based detection have significantly increased their use and have incr...

Heme enzymes are the most prominent category of iron-containing metalloenzymes with the capability of catalyzing an astonishingly wide range of reactions like epoxidation, hydroxylation, demethylation, desaturation, reduction, sulfoxidation, and decarboxylation. Various enzymes in this category are P450s, heme peroxidases, catalases, myoglobin, cytochrome C, and others. Besides this, the natural promiscuity and amenability of these enzymes to protein engineering and evolution have also added several non-native reactions such as C–H, N–H, S–H insertions, cyclopropanation, and other industrially important reactions to their capabilities. Surprisingly, all of these reactions and their wide substrate scopes are attributed to changes in the active site scaffold of different heme enzymes as the center of all enzymes is constituted by a porphyrin ring containing iron. Multiple prominent research groups across the world, including 2018, Nobel Laureate Frances Arnold's group, have shown keen interest in engineering and evolving these enzymes for utilizing their industrial potential. Besides engineering the active site, researchers have also explored the possibility of these enzymes catalyzing non-native reactions by replacing the center porphyrin ring with other cofactors or by changing the iron in the porphyrin ring with other metal ions along with engineering the active site and thereby creating novel artificial metalloenzymes. Thus, in this mini-review from our group, for the first time, we are trying to catalog various activities catalyzed by heme enzymes and their engineered variants and their active usage in various industries along with shedding light on their potential for use in various applications in the future.

Biocatalysts provide a major advantage to bio-based economy over chemical catalysts by catalyzing various useful transformations in an environment friendly manner along with other major benefits of selectivity, specificity, and low energy consumption. Since last decade, cellulase is the 3rd highest used enzyme in industry in various processes. Xylanase is also one amongst the widely used enzymes, and many industrial applications require synergistic action of both of these enzymes. These applications predominantly include bioethanol production, deinking of waste paper, animal feed processing, food processing, paper and pulp production, removal of fine fibers from textile material (biostoning), and pharmaceuticals. These enzymes are produced by microorganisms (fungi and bacteria), and hence, the microorganisms producing both cellulases and xylanases are in high demand by these industries. This review focuses on the synergistic applications of cellulase and xylanase enzymes across various industrial sectors. It also discusses the potential applications and the need of the microbial systems (fungi and bacteria) secreting both of these enzymes and the future prospects of their development into an integral part of various industrial processes.

Hemoproteins have recently emerged as promising biocatalysts for promoting a variety of carbene transfer reactions including cyclopropanation and Y—H insertion (Y = N, S, Si, B). For these and synthetic carbene transfer catalysts alike, achieving high chemoselectivity toward cyclopropanation in olefin substrates bearing unprotected Y—H groups has proven remarkably challenging due to competition from the more facile carbene Y—H insertion reaction. In this report, we describe the development of a novel artificial metalloenzyme based on an engineered myoglobin incorporating a serine-ligated Co-porphyrin cofactor that is capable of offering high selectivity toward olefin cyclopropanation over N—H and Si—H insertion. Intramolecular competition experiments revealed a distinct and dramatically altered chemoselectivity of the Mb(H64V,V68A,H93S)[Co(ppIX)] variant in carbene transfer reactions compared to myoglobin based variants containing the native histidine-ligated heme cofactor or other metal/proximal ligand substitutions. These studies highlight the functional plasticity of myoglobin as a ‘carbene transferase’ and illustrate how modulation of the cofactor environment within this metalloprotein scaffold represents a valuable strategy for accessing carbene transfer reactivity not exhibited by naturally occurring hemoproteins or transition metal catalysts.