A new method to determine optimum temperature and activation energies for enzymatic reactions

Trametes versicolor laccase activity modulated by the interaction with gold nanoparticles

In this study, the impact of gold nanoparticles (AuNPs) on the structure and activity of laccase from Trametes versicolor (Lc) was described. Fluorescence experiments revealed that AuNPs efficiently quench Lc's tryptophan fluorescence by a static and dynamic process. By using differential scanning microcalorimetry and circular dichroism spectroscopy, it was determined how the concentration of nanoparticles and the composition of the medium affected the secondary structure of Lc. The data revealed that upon binding with AuNPs, conformational changes take place mainly in presence of high amounts of nanoparticles. The complex kinetic analysis unveiled the Lc activity enhancement at low concentrations of AuNPs as opposed to the concentrated regime, where it can be reduced by up to 55%. The Michaelis-Menten tests highlighted that the activity of the biocatalyst is closely related to the concentration of AuNPs, while the Selwyn analysis demonstrated that even in a concentrated regime of Lc it is not deactivated regardless of the amount of AuNPs added. The thermal parameters improved by twofold in the presence of low AuNPs concentration, whereas the activation energy increased with AuNPs content, implying that not all collisions are beneficial to the enzyme structure. The effect of AuNPs on the decomposition of a recalcitrant dye (naphthol green B, NG) by Lc was also evaluated, and the Michaelis-Menten model revealed that only the high AuNPs content influenced negatively the Lc activity. The isothermal titration calorimetry revealed that hydrogen bonds are the main intermolecular forces between Lc and AuNPs, while electrostatic interactions are responsible for NG adsorption to AuNPs. The results of the docking analysis show the binding of NG near the copper T1 site of Lc with hydrogen bonds, electrostatic and hydrophobic interactions. The findings of this work provide important knowledge for laccase-based bio-nanoconjugates and their use in the field of environmental remediation.

Pharmacokinetics during therapeutic hypothermia in neonates: from pathophysiology to translational knowledge and physiologically-based pharmacokinetic (PBPK) modeling

INTRODUCTION

Perinatal asphyxia (PA) still causes significant morbidity and mortality. Therapeutic hypothermia (TH) is the only effective therapy for neonates with moderate to severe hypoxic-ischemic encephalopathy after PA. These neonates need additional pharmacotherapy, and both PA and TH may impact physiology and, consequently, pharmacokinetics (PK) and pharmacodynamics (PD).

AREAS COVERED

This review provides an overview of the available knowledge in PubMed (until November 2022) on the pathophysiology of neonates with PA/TH. In vivo pig models for this setting enable distinguishing the effect of PA versus TH on PK and translating this effect to human neonates. Available asphyxia pig models and methodological considerations are described. A summary of human neonatal PK of supportive pharmacotherapy to improve neurodevelopmental outcomes is provided.

EXPERT OPINION

To support drug development for this population, knowledge from clinical observations (PK data, real-world data on physiology), preclinical (in vitro and in vivo (minipig)) data, and molecular and cellular biology insights can be integrated into a predictive physiologically-based PK (PBPK) framework, as illustrated by the I-PREDICT project (Innovative physiology-based pharmacokinetic model to predict drug exposure in neonates undergoing cooling therapy). Current knowledge, challenges, and expert opinion on the future directions of this research topic are provided.

Tunning pectinase activity under the effects of electric fields in the enhanced clarification of wine must

Introduction

Pectinolytic enzymes are of great importance for the clarification process of “Vinho Verde” wine must, contributing to the reduction of haze development. During the last decade, a growing body of knowledge has been established about the effects of electric fields on the activation of important food enzymes. However, the influence of electrical parameters on catalytic activity is enzyme-dependent and should be evaluated on a case-by-case basis. This work describes, for the first time, the effects of electric fields and electrical frequency on the activity of pectinase (PEC) in the accelerated clarification of “Vinho Verde” must.

Method

Moderate electric fields (MEF) with intensities below 20 V/cm and at electrical frequencies ranging from 50 to 20 kHz were applied at temperatures between 15 and 35°C. Enzymatic activity was measured for 25 min, and the initial rate of reaction was determined by the coefficient of the linear plot of galacturonic acid (GAL) production as a function of time.

Results

The results show that electrical frequency can increase enzymatic activity depending on temperature conditions; at 20°C and with electrical frequencies of 2 and 20 kHz, enzymatic activity increased by up to 40 and 20%, respectively, when compared with the control sample (without the application of MEF). Temperature dependence was evaluated through the Arrhenius equation, showing that energy of activation (Ea) can be reduced from 9.2 to 6.6 kJ/mol at sub-optimal temperatures for PEC activity when MEF is applied.

Discussion

Electrical parameters, when combined with temperatures below 20°C, reduced pectin concentration in “Vinho Verde” wine must by up to 42% of its initial content. This emergent treatment can be integrated in relevant environmental conditions, presenting an opportunity to increase enzyme efficiency even in low-temperature conditions, which favors the winemaking process.

Determination of Activation Energies and the Optimum Temperatures of Hydrolysis of Starch by α-Amylase from Porcine Pancreas

The present paper reports the determination of the activation energies and the optimum temperatures of starch hydrolysis by porcine pancreas α-amylase. The parameters were estimated based on the literature data on the activity curves versus temperature for starch hydrolysis by α-amylase from porcine pancreas. It was assumed that both the hydrolysis reaction process and the deactivation process of α-amylase were first-order reactions by the enzyme concentration. A mathematical model describing the effect of temperature on porcine pancreas α-amylase activity was used. The determine deactivation energies Ea were from 19.82 ± 7.22 kJ/mol to 128.80 ± 9.27 kJ/mol, the obtained optimum temperatures Topt were in the range from 311.06 ± 1.10 K to 326.52 ± 1.75 K. In turn, the values of deactivation energies Ed has been noted in the range from 123.57 ± 14.17 kJ/mol to 209.37 ± 5.17 kJ/mol. The present study is related to the starch hydrolysis by α-amylase. In the industry, the obtained results the values Ea, Ed, Topt can be used to design and optimize starch hydrolysis by α-amylase porcine pancreas. The obtained results might also find application in research on the pharmaceutical preparations used to treat pancreatic insufficiency or prognosis of pancreatic cancer.

Modeling of enzymatic activity of free β-glucosidase from palm weevil, Rhynchophorus palmarum Linn. (Coleoptera: Curculionidae) larvae: Effects of pH and temperature

Palm weevil, Rhynchophorus palmarum L., is an important pest of palm trees (Elaeis guineensis) around the tropical regions. Characterization of their digestive enzymes could be an important stage to develop appropriate pest control strategies. Study of these enzymes could also be of interest in different biotechnological applications. Among digestive enzymes, there is β-glucosidase which hydrolytically catalyzes the β-glycosidic linkage of glycosides. In the present work, the catalytic activity of β-glucosidase in the digestive juice of last larval instar of R. palmarum L. (Rpbgl) has been investigated using p-nitrophenyl-β-D-glucopyranoside (pNPG) as substrate. The "classical" physico-chemical properties for purified Rpbgl have been determined by the help of enzymatic activity modeling. Thus, the values of (325.4 ± 0.2) K, 5.28 ± 0.07 and (37.9 ± 0.6) kJ mol^-1 were obtained for optimum temperature, optimum pH and activation energy, respectively. The pK values for enzyme-substrate complex are 4.25 ± 0.07 and 6.20 ± 0.07 for nucleophile and the proton donor, respectively. Enzyme kinetics study was also performed and the values of (127 ± 6) U mg^-1 and (0.78 ± 0.08) mM were obtained for V_max and K_m, respectively. Using the Equilibrium model (EM), the thermal inactivation data were analyzed. ΔH_eq, T_eq, ΔG_inact^∗ and ΔG_cat^∗ were found to be (222 ± 4) kJ mol^-1, (323.0 ± 0.1) K, (101.9 ± 0.2) kJ mol^-1 and (53.37 ± 0.02) kJ mol^-1, respectively. These results show that Rpbgl is less stable with a narrow temperature tolerance compared to other β-glucosidases.

Stochastic modelling of cellulose hydrolysis with Gauss and Weibull distributed transition probabilities

Two Markov-type stochastic models were developed to describe the kinetics of acid hydrolysis of cellulose. One of them involved a Gauss (normal) distribution of probabilities of chemical bond breaking, the other a Weibull distribution. It was considered that the random breaking of cellulose was based on the cleavage of a parent macromolecule into two descendants. Model equations and kinetics of acid hydrolysis of cellulose consisting of 10 and 100 units of cellobiose were presented. The effects of acid concentration and temperature on the kinetics of hydrolysis process were taken into account. The results obtained applying both stochastic models were in a reasonable agreement with those obtained using a deterministic kinetic model. These stochastic models can accurately describe the kinetics of acid hydrolysis and cover the drawbacks of some deterministic kinetic models, e.g., large number of model equations and parameters, modification of parameter values by changing the process conditions.

An integrated strategy for the effective production of bristle protein hydrolysate by the keratinolytic filamentous bacterium Amycolatopsis keratiniphila D2

In a conventional microorganism-mediated biological process for degradation of keratinous waste material the production of keratin-specific proteases (i.e., keratinases) and the hydrolysis of keratin-rich residual biomass both take place during the same stage of the bioprocess and, as a consequence, occur simultaneously under suboptimal conditions. In the present study the keratinolytic actinomycete Amycolatopsis keratiniphila D2 was successfully employed to biodegrade thermally pretreated porcine bristles at high solids loading (16% w/v) via a novel cultivation methodology. Indeed, the two-stage submerged fermentation process developed in this work enabled to efficiently recover, in a single unit operation, about 73% of the protein material contained in the keratinous biowaste structure, resulting in an overall accumulation of 89.3 g·L^-1 protein-rich hydrolysate and a productivity of 427 mg crude soluble proteins per litre per hour. The obtained protein hydrolysate powder displayed a 2.2-fold increase in its in vitro pepsin digestibility (95%) with respect to the non-hydrolysed pretreated substrate (43%). In addition, the chromatogram obtained by size-exclusion chromatography analysis of the final product indicated that, among the identified fractions, those consisting of small peptides and free amino acids were the most abundantly present inside the analysed sample. Given these facts it is possible to conclude that the soluble proteins, peptides and free amino acids recovered through the newly designed two-stage bioextraction process could represent a viable alternative source of protein in animal feed formulation.

Genome-wide identification and biochemical characterization of the UGT88F subfamily in Malus x domestica Borkh

The UDP-glycosyltransferase UGT88F subfamily has been described first in Malus x domestica with the characterization of UGT88F1. Up to now UGT88F1 was one of the most active UGT glycosylating dihydrochalcones in vitro. The involvement of UGT88F1 in phloridzin (phloretin 2'-O-glucoside) synthesis, the main apple tree dihydrochalcone, was further confirmed in planta. Since the characterization of UGT88F1, this new UGT subfamily has been poorly studied probably because it seemed restricted to Maloideae. In the present study, we investigate the apple tree genome to identify and biochemically characterize the whole UGT88F subfamily. The apple tree genome contains five full-length UGT88F genes out of which three newly identified members (UGT88F6, UGT88F7 and UGT88F8) and a pseudogene. These genes are organized into two genomic clusters resulting from the recent global genomic duplication event in the apple tree. We show that recombinant UGT88F8 protein specifically glycosylates phloretin in the 2'OH position to synthetize phloridzin in vitro and was therefore named UDP-glucose: phloretin 2'-O-glycosyltransferase. The Km values of UGT88F8 are 7.72 μM and 10.84 μM for phloretin and UDP-glucose respectively and are in the same range as UGT88F1 catalytic parameters thus constituting two isoforms. Co-expression patterns of both UGT88F1 and UGT88F8 argue for a redundant function in phloridzin biosynthesis in planta. Contrastingly, recombinant UGT88F6 protein is able to glycosylate in vitro a wide range of flavonoids including flavonols, flavones, flavanones, chalcones and dihydrochalcones, although flavonols are the preferred substrates, e.g. Km value for kaempferol is 2.1 μM. Depending on the flavonoid, glycosylation occurs at least on the 3-OH and 7-OH positions. Therefore UGT88F6 corresponds to an UDP-glucose: flavonoid 3/7-O-glycosyltransferase. Finally, a molecular modeling study highlights a very high substitution rate of residues in the acceptor binding pocket between UGT88F8 and UGT88F6 which is responsible for the enzymes divergence in substrate and regiospecificity, despite an overall high protein homology.