skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: A High‐Throughput in Vitro Assay System for the Detection of the Enzymatic Dihydroxylation of Aliphatic Olefins
Abstract Rieske dioxygenase enzymes can perform thecis‐dihydroxylation of aliphatic olefins, representing a potential green alternative to established methods of performing this important transformation. However, the activity of the natural enzymes in this context is low relative to their more well‐known activity in thecis‐dihydroxylation of aromatics. To enable the engineering of dioxygenase enzymes for improved activity in the dihydroxylation of aliphatic olefins, we have developed an assay system to detect the relevant diol metabolites produced from whole‐cell fermentation cultures. Optimization studies were carried out to maximize the sensitivity of the assay system, and its utility in thein vitroscreening of enzyme variant libraries was demonstrated. The assay system was utilized in screening studies that identified Rieske dioxygenase variants with significantly improved activity in the dihydroxylation of aliphatic olefins relative to the wild‐type enzyme.  more » « less
Award ID(s):
2147098
PAR ID:
10575515
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Advanced Synthesis and Catalysis
Date Published:
Journal Name:
Advanced Synthesis & Catalysis
Volume:
366
Issue:
21
ISSN:
1615-4150
Page Range / eLocation ID:
4392 to 4398
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract Rieske dioxygenases have a long history of being utilized as green chemical tools in the organic synthesis of high‐value compounds, due to their capacity to perform thecis‐dihydroxylation of a wide variety of aromatic substrates. The practical utility of these enzymes has been hampered however by steric and electronic constraints on their substrate scopes, resulting in limited reactivity with certain substrate classes. Herein, we report the engineering of a widely used member of the Rieske dioxygenase class of enzymes, toluene dioxygenase (TDO), to produce improved variants with greatly increased activity for thecis‐dihydroxylation of benzoates. Through rational mutagenesis and screening, TDO variants with substantially improved activity over the wild‐type enzyme were identified. Homology modeling, docking studies, molecular dynamics simulations, and substrate tunnel analysis were applied in an effort to elucidate how the identified mutations resulted in improved activity for this polar substrate class. These analyses revealed modification of the substrate tunnel as the likely cause of the improved activity observed with the best‐performing enzyme variants. 
    more » « less
  2. Rieske dioxygenases are multi-component enzyme systems, naturally found in many soil bacteria, that have been widely applied in the production of fine chemicals, owing to the unique and valuable oxidative dearomatization reactions they catalyze. The range of practical applications for these enzymes in this context has historically been limited, however, due to their limited substrate scope and strict selectivity. In an attempt to overcome these limitations, our research group has employed the tools of enzyme engineering to expand the substrate scope or improve the reactivity of these enzyme systems in specific contexts. Traditionally, enzyme engineering campaigns targeting metalloenzymes have avoided mutations to metal-coordinating residues, based on the assumption that these residues are essential for enzyme activity. Inspired by the success of other recent enzyme engineering reports, our research group investigated the potential to alter or improve the reactivity of Rieske dioxygenases by altering or eliminating iron coordination in the active site of these enzymes. Herein, we report the modification of all three iron-coordinating residues in the active site of toluene dioxygenase both to alternate residues capable of coordinating iron, and to a residue that would eliminate iron coordination. The enzyme variants produced in this way were tested for their activity in the cis-dihydroxylation of a small library of potential aromatic substrates. The results of these studies demonstrated that all three iron-coordinating residues, in their natural state, are essential for enzyme activity in toluene dioxygenase, as the introduction of any mutations at these sites resulted in a complete loss of cis-dihydroxylation activity. 
    more » « less
  3. Abstract Protein acetylation and acylation are widespread post‐translational modifications (PTMs) in eukaryotic and prokaryotic organisms. Histone acetyltransferase (HATs) enzymes catalyze the addition of short‐chain acyl moieties to lysine residues on cellular proteins. Many HAT members are found to be dysregulated in human diseases, especially oncological processes. Screening potent and selective HAT inhibitors has promising application for therapeutic innovation. A biochemical assay for quantification of HAT activity utilizing luminescent output is highly desirable to improve upon limitations associated with the classic radiometric assay formats. Here we report the design of a bioluminescent technological platform for robust and sensitive quantification of HAT activity. This platform utilizes the metabolic enzyme acetyl‐CoA synthetase 1 (ACS1) for a coupled reaction with firefly luciferase to generate luminescent signal relative to the HAT‐catalyzed acetylation reaction. The biochemical assay was implemented in microtiter plate format and our results showed this assay sensitively detected catalytic activity of HAT enzyme p300, accurately measured its steady‐state kinetic parameters of histone acetylation and measured the inhibitory potency of HAT inhibitor. This platform demonstrated excellent robustness, reproducibility, and signal‐to‐background ratios, with a screening window Z’=0.79. Our new bioluminescent design provides an alternative means for HAT enzymatic activity quantitation and HAT inhibitor screening. 
    more » « less
  4. Fervidibacter sacchariis an aerobic hyperthermophile belonging to the phylumArmatimonadotathat degrades a variety of polysaccharides. Its genome encodes 117 enzymes with one or more annotated glycoside hydrolase (GH) domain, but the roles of these putative GHs in polysaccharide catabolism are poorly defined. Here, we describe oneF. saccharienzyme encoding a GH10 domain, Fsa02490Xyn, that was previously shown to be active onMiscanthus, oat β‐glucan, and beech‐wood xylan, with optimal activity at 90–100 °C. We show that Fsa02490Xyn is also active on birch‐wood xylan and gellan gum. The pH range on beech‐wood xylan was 4.5 to 9.5 (pHopt7.0–8.0). Fsa024940Xyn had aKmof 2.375 mm,Vmaxof 1250 μm·min−1, andkcat/Kmof 1.259 × 104 s−1·m−1when using apara‐nitrophenyl‐𝛽‐xylobioside assay. A phylogenetic analysis of GH10 family enzymes revealed a large clade of enzymes from diverse members of the classFervidibacteria, including Fsa02490Xyn and a second enzyme fromF. sacchari, with apparent horizontal gene transfer withinFervidibacteriaand betweenFervidibacteriaand thermophilicBacillota. This study establishes Fsa02490Xyn as a hyperthermophilic GH10 enzyme with endo‐β‐1,4‐xylanase activity and identifies a large clade of homologous GH10 enzymes within the classFervidibacteria. Impact statementThe depolymerization of xylan at high temperatures is important because this process limits the degradation of polysaccharides in nature and the synthesis of biofuels from plant wastes. Our study is also important becauseF. sacchariis one of only a few cultivated members of theArmatimonadota, which are polysaccharide‐degradation specialists. 
    more » « less
  5. Abstract: A colorimetric indicator displacement assay (IDA) amenable to high-throughput experimentation was developed to determine the percentage of cis and trans alkenes. Using 96-well plates two steps are performed: a reaction plate for dihydroxylation of the alkenes followed by an IDA screening plate consisting of an indicator and a boronic acid. The dihydroxylation generates either erythro or threo vicinal diols from cis or trans alkenes, depending upon their syn- or antiaddition mechanisms. Threo diols preferentially associate with the boronic acid due to the creation of more stable boronate esters, thus displacing the indicator to a greater extent. The generality of the protocol was demonstrated using seven sets of cis and trans alkenes. Blind mixtures of cis and trans alkenes were made, resulting in an average error of 2% in the percentage of cis or trans alkenes, and implementing E2 and Wittig reactions gave errors of 3%. Furthermore, we developed variants of the IDA for which the color may be tuned to optimize the response for the human eye. 
    more » « less