Unexpectedly enhanced stereoselectivity of peroxidase-catalyzed sulfoxidation in branched alcohols

Improvement of kinetic properties and thermostability of recombinant Lepidium draba peroxidase (LDP) upon exposed to osmolytes

In this study, effects of different concentrations of glycine and D-sorbitol were analyzed on the activity and thermostability of recombinant Lepidium draba peroxidase (LDP). Based on the results, activity of the enzyme increased in the presence of various concentrations of these osmolytes. Maximum activity was detected for the enzyme in the presence of 300 mM glycine and 600 mM sorbitol. In presence of the aforementioned doses of osmolytes, enzyme affinity for substrate (3,3',5,5'-tetramethylbenzidine and H₂O₂) and V_max increased. According to the results, enzyme stability improved against temperature and H₂O₂. Furthermore, structural changes of the enzyme upon exposure to the osmolytes were revealed by the use of far-UV circular dichroism and fluorescence methods. The results showed, whereas the secondary structure of the enzyme was not significantly changed upon exposed to the osmolytes, the fluorescence studies revealed microenvironment of the aromatic residues dramatically affected by them. Overall, it may be speculated, structural changes of the enzyme upon exposed to the osmolytes, lead to the improvement of its kinetic properties and stability that can be benefit for using of it in in vitro applications.

Specific oxyfunctionalisations catalysed by peroxygenases: opportunities, challenges and solutions

Peroxygenases are promising oxyfunctionalisation catalysts for organic synthesis.

Horseradish peroxidase (HRP) as a tool in green chemistry

The horseradish peroxidase (HRP) potential in organic synthesis.

Validation of a two-parameter quantitative structure–activity relationship as a legitimate tool for rational re-design of horseradish peroxidase

Previously reported rates of reaction between six mutant strains of the enzyme horseradish peroxidase (HRP) and a test substrate, 2-methoxyphenol, were found to correlate with characteristic binding distances computed using molecular simulation. The correlation (R(2) = 0.86) bears out a working hypothesis that, based on a quantitative structure-activity relationship (QSAR) we had previously developed for HRP, reductions in binding distances between the HRP enzyme and any selected substrate mediate increased enzyme reactivity towards that substrate. The results validate the use of QSAR as a quantitative means for formulating enzyme mutations designed to achieve enhanced HRP reactivity towards compounds of specific interest.

Quantitative structure-activity relationship based quantification of the impacts of enzyme-substrate binding on rates of peroxidase-mediated reactions of estrogenic phenolic chemicals

The initial rates of horseradish peroxidase (HRP)-mediated enzymatic reactions of 15 assorted aqueous phase phenolic chemicals were studied. The associated reaction rate constants were found to correlate quantitatively with two independent variables: the highest-occupied molecular orbital energy (E(HOMO)) defining the intrinsic redox reactivities of the phenolic substrates and the distance between a substrate and the deltaN of HIS42's imidazole ring in an HRP/substrate binding complex, obtained through molecular simulations. Highly correlated quantitative structure-activity relationship (QSAR) equations were thus developed. This work provides insights into the impacts that HRP/substrate binding may have on HRP-mediated reactions. Additionally, the QSAR equations developed in the work may serve as a basis to further explore the potential use of HRP-mediated reactions in the treatment of estrogenic contaminants, and they constitute an important tool for redesign and screening of potential proteomic modifications to the wild-type HRP structure intended to enhance reactivity toward selected substrates.

Tailoring of horseradish peroxidase activity in cationic water-in-oil microemulsions

Horseradish peroxidase (HRP) in cationic water-in-oil (W/O) microemulsions has always been ignored in reverse micellar enzymology, mainly because cationic surfactants are inhibitors of enzyme peroxidase. In the present study, for the first time, we have successfully introduced the cationic W/O microemulsion as an attractive host for efficient HRP activity. To this notion, much improved activity of HRP was observed in the W/O microemulsion of cetyltrimethylammonium bromide (CTAB) with an increase in n-hexanol concentration and W0 ([water]/[surfactant]), presumably due to the increased interfacial area of the microemulsions. In support of our above observation, six surfactants were synthesized with an increased headgroup size where the methyl groups of CTAB were subsequently replaced by the n-propyl and 2-hydroxyethyl groups, respectively, to prepare mono-, di-, and tripropylated/hydroxyethylated n-hexadecylammonium bromide. The peroxidase activity enhanced with headgroup size and also followed an overall trend similar to that found in the case of CTAB. Possibly, the reduced positive charge density at the augmented interfacial area by means of increase, either in headgroup size, cosurfactant concentration, and/or W0, is not capable of inactivating HRP. Also, the larger space at the interface may facilitate easier solubilization of the enzyme and increase the local concentration of enzyme and substrate, leading to the higher activity of HRP. The best activity was obtained with surfactant N-hexadecyl-N,N,N-tripropylammonium bromide, the highest ever found in any cationic W/O microemulsions, being almost 3 times higher than that found in water. Strikingly, this observed highest activity is comparable with that observed in an anionic bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT)-based system, the best W/O microemulsions used for HRP.

Co-lyophilization with d-proline Greatly Enhances Peroxidase’s Stereoselectivity in a Non-aqueous Medium

The impact of co-lyophilizing horseradish peroxidase (HRP) with numerous amino acids and other chiral excipients on the enzyme's subsequent stereoselectivity [E(S/R)] in the sulfoxidation of thioanisole in 2-propanol was systematically investigated. While many improved the stereoselectivity of (and significantly activated) HRP, the greatest effect was observed with D-proline which enhanced the E(S/R) value by over an order of magnitude from synthetically meaningless to useful.

Asymmetric enzymatic oxidoreductions in organic solvents

It is now beyond doubt that enzymes can vigorously work even in neat organic solvents containing little or no water. Switching the enzymatic reaction medium from aqueous to nonaqueous can make previously problematic processes feasible through, for example, increased substrate solubility or diminished side reactions. Moreover, when placed in this highly unnatural milieu, enzymes exhibit new and potentially valuable properties, including greater stability, markedly altered selectivity that can be readily controlled by the solvent, and molecular memory. Consequently, novel synthetic and biotechnological opportunities ensue, as illustrated herein by those based on enzymatic oxidoreductions such as the asymmetric peroxidase-catalyzed sulfoxidation of organic sulfides.