Recent advances on protein–polysaccharide electrostatic complex and coacervates' formation, structure and properties are presented. The first section emphasises on the thermodynamics of complexes formation, the contribution of enthalpic and entropic effects is specifically discussed. Then, their structure is described at different length scales and recent findings on the phase-ordering dynamics of complex and coacervates formation are covered. Finally, the most relevant functional properties of protein–polysaccharide complexes and coacervates for food applications are described.

Protein–polysaccharide complexes and coacervates

Abstract Recent advances on protein–polysaccharide electrostatic complex and coacervates' formation, structure and properties are presented. The first section emphasises on the thermodynamics of complexes formation, the contribution of enthalpic and entropic effects is specifically discussed. Then, their structure is described at different length scales and recent findings on the phase-ordering dynamics of complex and coacervates formation are covered. Finally, the most relevant functional properties of protein–polysaccharide complexes and coacervates for food applications are described.

Protein-polysaccharide complexes and coacervates.

ω-Transaminases for the synthesis of non-racemic α-chiral primary amines

The interactions of proteins and polyelectrolytes lead to diverse applications in separations, delivery and wound repair, and are thus of interest to scientists in e.g. (a) glycobiology, (b) tissue engineering, (c) biosensing, and (d) pharmacology. This breadth is accompanied by an assortment of contexts and models in which polyelectrolytes are seen as (a) protein cognates assisting in complex cellular roles, (b) surrogates for the extracellular matrix, mimicking its hydration, mechanical and sequestering properties, (c) benign hosts that gently entrap, deposit and tether protein substrate specificity, and (d) selective but non-specific agents that modify protein solubility. Unsurprisingly, this literature is somewhat segregated by objectives and paradigms. We hope this review, which emphasizes publications over the last 8 years, represents and also counterbalances that divergence. An ongoing theme is the role of electrostatics, and we show how this leads to the variety of physical forms taken by protein–polyelectrolyte complexes. We present approaches towards analysis and characterization, motivated by the goal of structure–property elucidation. Such understanding should guide in applications, our third topic. We present recent developments in modeling and simulations of protein–polyelectrolyte systems. We close with a prospective on future developments in this field.

/pdf/protein-polyelectrolyte-interactions-3iskvzeg8j.pdf

Protein–polyelectrolyte interactions

Optically active amines and amino acids play an important role in the pharmaceutical, agrochemical, and chemical industries. They are frequently used as synthons for the preparation of various pharmaceutically active substances and agrochemicals, but also as resolving agents to obtain chiral carboxylic acids. Consequently, there is a need for efficient methods to obtain the desired enantiomer of a given target structure in optically pure form. Beside a range of chemical methods using for example, asymmetric synthesis with transition metal catalysts, enzymes represent a useful alternative to access this important class of compounds. This review covers biocatalytic approaches using hydrolases (i.e. lipases, amidases), monoamine oxidase and other enzymes. Special focus is given on the application of ω-transaminases with emphasis on concepts to allow efficient asymmetric synthesis starting from prostereogenic ketones.

Biocatalytic Routes to Optically Active Amines

Aminotransferases (ATs) have useful applications in the chemical industry because of their capability of introducing amino group into ketones or keto acids as well as their high enantioselectivity and regioselectivity and broad substrate specificity Abundant protein sequence databases and new powerful tools such as advanced computational structure modeling, multiple sequence analysis, and in vitro evolution have made it possible to understand the detailed reaction mechanisms of various ATs and to isolate and design novel enzymes for unnatural substrates This, in turn, suggests that developing new integrated approaches to screen ATs are possible, but at the same time poses formidable technical challenges Here, this paper reviews the use of family profile analysis to find the correlation between the type of ATs and their substrate specificities, the relation between the 3-D structures of ATs and their substrate specificities, and enzyme engineering for the synthesis of unnatural substrates

Revisit of aminotransferase in the genomic era and its application to biocatalysis

A novel high-throughput screening method that overcame product inhibition was used to isolate a mutant omega-transaminase from Vibrio fluvialis JS17. An enzyme library was generated using error-prone PCR mutagenesis and then enriched on minimal medium containing 2-aminoheptane as the sole nitrogen source and 2-butanone as an inhibitory ketone. An identified mutant enzyme, omega-TAmla, showed significantly reduced product inhibition by aliphatic ketone. The product inhibition constants of the mutant with 2-butanone and 2-heptanone were 6- and 4.5-fold higher than those of the wild type, respectively. Using omega-TAmla (50 U/ml) overexpressed in Escherichia coli BL21, 150 mM 2-aminoheptane was successfully resolved to (R)-2-aminoheptane (enantiomeric excess, >99%) with 53% conversion with an enantioselectivity of >100.

/pdf/use-of-enrichment-culture-for-directed-evolution-of-the-8lc0sd6qu7.pdf

Use of Enrichment Culture for Directed Evolution of the Vibrio fluvialis JS17 ω-Transaminase, Which Is Resistant to Product Inhibition by Aliphatic Ketones

A simultaneous synthesis of (R)-1-phenylethanol and (R)-α-methylbenzylamine from racemic α-methylbenzyl- amine was achievied using an ω-transaminase, alcohol dehydrogenase, and glucose dehydrogenase in a coupled reaction. Racemic α-methylbenzylamine (100 mM) was converted to 49 mM (R)-1-phenylethanol (> 99% ee) and 48 mM (R)-α-methylbenzylamine (> 98% ee) in 18 h at 37 °C. This method was also used to overcome product inhibition of ω-TA by the ketone product in the kinetic resolution of racemic amines at high concentration.

Simultaneous synthesis of enantiomerically pure (R)-1-phenylethanol and (R)-α-methylbenzylamine from racemic α-methylbenzylamine using ω-transaminase/alcohol dehydrogenase/glucose dehydrogenase coupling reaction

High-throughput screening method for the identification of active and enantioselective ω-transaminases

https://www.cell.com/cell-chemical-biology/pdf/S1074-5521(04)00164-4.pdf

Bum-Yeol Hwang

Papers

Revisit of aminotransferase in the genomic era and its application to biocatalysis

Use of Enrichment Culture for Directed Evolution of the Vibrio fluvialis JS17 ω-Transaminase, Which Is Resistant to Product Inhibition by Aliphatic Ketones

Simultaneous synthesis of enantiomerically pure (R)-1-phenylethanol and (R)-α-methylbenzylamine from racemic α-methylbenzylamine using ω-transaminase/alcohol dehydrogenase/glucose dehydrogenase coupling reaction

High-throughput screening method for the identification of active and enantioselective ω-transaminases

Characterization and Investigation of Substrate Specificity of the Sugar Aminotransferase WecE from E. coli K12