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Selectivity of enzymes involved in the formation of opposite enantiomeric series of p-menthane monoterpenoids in peppermint and Japanese catnip.
Srividya, N, Lange, I, Richter, JK, Wüst, M, Lange, BM
Plant science : an international journal of experimental plant biology. 2022;:111119
Abstract
Peppermint (Mentha x piperita L.) and Japanese catnip (Schizonepeta tenuifolia (Benth.) Briq.) accumulate p-menthane monoterpenoids with identical functionalization patterns but opposite stereochemistry. In the present study, we investigate the enantioselectivity of multiple enzymes involved in monoterpenoid biosynthesis in these species. Based on kinetic assays, mint limonene synthase, limonene 3-hydroxylase, isopiperitenol dehydrogenase, isopiperitenone reductase, and menthone reductase exhibited significant enantioselectivity toward intermediates of the pathway that proceeds through (-)-4S-limonene. Limonene synthase, isopiperitenol dehydrogenase and isopiperitenone reductase of Japanese catnip preferred intermediates of the pathway that involves (+)-4R-limonene, whereas limonene 3-hydroxylase was not enantioselective, and the activities of pulegone reductase and menthone reductase were too low to acquire meaningful kinetic data. Molecular modeling studies with docked ligands generally supported the experimental data obtained with peppermint enzymes, indicating that the preferred enantiomer was aligned well with the requisite cofactor and amino acid residues implicated in catalysis. A striking example for enantioselectivity was peppermint (-)-menthone reductase, which binds (-)-menthone with exquisite affinity but was predicted to bind (+)-menthone in a non-productive orientation that positions its carbonyl functional group at considerable distance to the NADPH cofactor. The work presented here lays the groundwork for structure-function studies aimed at unraveling how enantioselectivity evolved in closely related species of the Lamiaceae and beyond.
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2.
Mechanisms for enzymatic reduction of nitric oxide to nitrous oxide - A comparison between nitric oxide reductase and cytochrome c oxidase.
Blomberg, MRA, Ädelroth, P
Biochimica et biophysica acta. Bioenergetics. 2018;(11):1223-1234
Abstract
Cytochrome c oxidases (CcO) reduce O2 to H2O in the respiratory chain of mitochondria and many aerobic bacteria. In addition, some species of CcO can also reduce NO to N2O and water while others cannot. Here, the mechanism for NO-reduction in CcO is investigated using quantum mechanical calculations. Comparison is made to the corresponding reaction in a "true" cytochrome c-dependent NO reductase (cNOR). The calculations show that in cNOR, where the reduction potentials are low, the toxic NO molecules are rapidly reduced, while the higher reduction potentials in CcO lead to a slower or even impossible reaction, consistent with experimental observations. In both enzymes the reaction is initiated by addition of two NO molecules to the reduced active site, forming a hyponitrite intermediate. In cNOR, N2O can then be formed using only the active-site electrons. In contrast, in CcO, one proton-coupled reduction step most likely has to occur before N2O can be formed, and furthermore, proton transfer is most likely rate-limiting. This can explain why different CcO species with the same heme a3-Cu active site differ with respect to NO reduction efficiency, since they have a varying number and/or properties of proton channels. Finally, the calculations also indicate that a conserved active site valine plays a role in reducing the rate of NO reduction in CcO.
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3.
Leishmania donovani pteridine reductase 1: comparative protein modeling and protein-ligand interaction studies of the leishmanicidal constituents isolated from the fruits of Piper longum.
Sahi, S, Tewatia, P, Ghosal, S
Journal of molecular modeling. 2012;(12):5065-73
Abstract
Visceral leishmaniasis or kala-azar is caused by the dimorphic parasite Leishmania donovani in the Indian subcontinent. Treatment options for kala-azar are currently inadequate due to various limitations. Currently, drug discovery for leishmaniases is oriented towards rational drug design; the aim is to identify specific inhibitors that target particular metabolic activities as a possible means of controlling the parasites without affecting the host. Leishmania salvages pteridin from its host and reduces it using pteridine reductase 1 (PTR1, EC 1.5.1.33), which makes this reductase an excellent drug target. Recently, we identified six alkamides and one benzenoid compound from the n-hexane fraction of the fruit of Piper longum that possess potent leishmanicidal activity against promastigotes as well as axenic amastigotes. Based on a homology model derived for recombinant pteridine reductase isolated from a clinical isolate of L. donovani, we carried out molecular modeling and docking studies with these compounds to evaluate their binding affinity. A fairly good agreement between experimental data and the results of molecular modeling investigation of the bioactive and inactive compounds was observed. The amide group in the conjugated alkamides and the 3,4-methylenedioxystyrene moiety in the benzenoid compound acts as heads and the long aliphatic chain acts as a tail, thus playing important roles in the binding of the inhibitor to the appropriate position at the active site. The remarkably high activity of a component containing piperine and piperine isomers (3.36:1) as observed by our group prompted us to study the activities of all four isomers of piperine-piperine (2E,4E), isopiperine (2Z,4E), isochavicine (2E,4Z), and chavicine (2Z,4Z)-against LdPTR1. The maximum inhibitory effect was demonstrated by isochavicine. The identification of these predicted inhibitors of LdPTR1 allowed us to build up a stereoview of the structure of the binding site in relation to activity, affording significant information that should prove useful during the structure-based design of leishmanicidal drugs.
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4.
Specific and pronounced impacts of lisinopril and lisinopril plus simvastatin on erythrocyte antioxidant enzymes.
Kaminsky, Y, Suslikov, A, Kosenko, E
Journal of clinical pharmacology. 2010;(2):180-7
Abstract
Angiotensin-converting enzyme inhibitors are effective at reducing blood pressure, whereas statins decrease plasma cholesterol impeding atherosclerosis. It is hypothesized that these medications may improve blood pressure and serum cholesterol by modifying the antioxidative status and energy metabolism of erythrocytes. In this study, the effects of 2 treatments are compared: lisinopril alone versus lisinopril + simvastatin, on erythrocyte antioxidant and energy metabolic enzymes. Patients with atherosclerosis and moderate hypertension are randomly assigned to receive lisinopril 10 to 20 mg/d or lisinopril 10 to 20 mg/d plus simvastatin 20 mg/d for 24 weeks. Higher catalase activity and lower glutathione peroxidase activity are observed in 94% to 100% patients from both groups after 12 and 24 weeks of treatment. Superoxide dismutase activity is increased significantly only after 24 weeks. No changes of glutathione reductase, lactate dehydrogenase, and phosphofructokinase activities are found under any conditions indicated. Both treatments decrease systolic and diastolic blood pressure equally. Only lisinopril + simvastatin treatment decreases plasma total cholesterol and low-density lipoprotein cholesterol. The results show for the first time that lisinopril monotherapy and combined lisinopril + simvastatin therapy exhibit specific and pronounced effects on antioxidant and energy metabolic enzyme activities in erythrocytes of hypertensive patients.
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5.
Oxidation of maltose and trehalose during prolonged moderate-intensity exercise.
Venables, MC, Brouns, F, Jeukendrup, AE
Medicine and science in sports and exercise. 2008;(9):1653-9
Abstract
PURPOSE The aim of the present study was to compare the effects of trehalose (TRE) and maltose (MAL) ingestion on exogenous carbohydrate oxidation rates and blood metabolite responses during prolonged moderate-intensity cycling exercise. METHODS Nine trained subjects performed three randomly assigned bouts of exercise separated by at least 1 wk. Each trial consisted of 150 min of cycling at 55% of maximal power output (Wmax) while ingesting a solution providing either 1.1 g x min(-1) TRE, 1.1 g x min(-1) MAL, or water (WAT). RESULTS Total carbohydrate oxidation rates were significantly higher (P < 0.05) in both the MAL (2.09 +/- 0.18 g x min(-1)) and TRE (1.92 +/- 0.32 g x min(-1)) trials compared with the WAT trial (1.62 +/- 0.28 g x min(-1)). Peak exogenous carbohydrate oxidation was significantly higher in the MAL trial compared with the TRE trial (1.01 +/- 0.24 and 0.73 +/- 0.22 g x min(-1), respectively, P < 0.05). The MAL trial resulted in significantly reduced endogenous carbohydrate oxidation rates compared with the WAT trial (1.20 +/- 0.25 and 1.62 +/- 0.28 g x min(-1), respectively, P < 0.05). When compared with the WAT trial, total fat oxidation for the same period was significantly reduced in both carbohydrate trials (0.91 +/- 0.19, 0.68 +/- 0.19, and 0.79 +/- 0.19 g x min(-1) for WAT, MAL, and TRE, respectively, P < 0.05) and tended to be lower in MAL compared with TRE (P < 0.06). DISCUSSION Both solutions maintained high plasma glucose concentrations. MAL had a "sparing" effect on endogenous carbohydrate stores. The reduced exogenous carbohydrate oxidation rate of TRE compared to MAL is probably due to a reduced enzymatic hydrolysis rate within the small intestine, causing a slower availability.
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6.
Measurement of chlorite dismutase activities in perchlorate respiring bacteria.
Xu, J, Logan, BE
Journal of microbiological methods. 2003;(2):239-47
Abstract
Chlorite dismutase (CD) catalyzes the disproportionation of chlorite to chloride (ClO(2)(-)-->Cl(-)+O(2)) and is present in bacteria capable of cell respiration using perchlorate or chlorate. The activity of this enzyme has previously been measured by monitoring oxygen evolution using a Clark-type dissolved oxygen (DO) probe. We demonstrate here, using two other methods to measure CD activity (a chloride-specific electrode and ion chromatography (IC)) via chloride production, that the DO probe method underestimates dismutation rates. Of the three methods, the chloride probe was the easiest to use and did not require extensive sample handling or post-experimental analysis. Using the chloride electrode method, we determined whole cell rate constants (V(max)=64 U/mg DW, K(m)=0.17 mM) for the chlorate-grown suspensions of Dechlorosoma sp. strain KJ. We compared the CD activities of strain KJ at a fixed chlorite concentration (0.6 mM) to four other perchlorate respiring bacteria (PRB), and to one non-PRB (Pseudomonas aeruginosa). Chlorate-grown cultures of the five PRB strains had CD activities ranging from 25 to 50 U/mg of cell dry weight (DW), while aerobically grown cultures of the PRB had much lower CD activities (0.5-4 U/mg DW). To our knowledge, this is the first systematic comparison of the different methods to measure CD activities, and the first comparison of CD activities of different PRBs.
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7.
Structure-function relationships in flavoenzyme-dependent amine oxidations: a comparison of polyamine oxidase and monoamine oxidase.
Binda, C, Mattevi, A, Edmondson, DE
The Journal of biological chemistry. 2002;(27):23973-6
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8.
Comparison between the nitric oxide reductase family and its aerobic relatives, the cytochrome oxidases.
de Vries, S, Schröder, I
Biochemical Society transactions. 2002;(4):662-7
Abstract
The denitrification pathway has been studied in the hyperthermophilic archaeon Pyrobaculum aerophilum. In contrast with Gram-negative bacteria, all four denitrification enzymes are membrane-bound. P. aerophilum is also the only denitrifyer identified so far in which menaquinol is the electron donor to all four denitrification reductases. The NO reductase (NOR) of P. aerophilum belongs to the superfamily of haem-copper oxidases and is of the qNOR (quinol-dependent) type. Three types of NOR have been purified so far: cNOR (cytochrome c/pseudoazurin-dependent), qNOR and qCu(A)NOR (qNOR that contains Cu(A) at the electron entry site). It is proposed that the NORs and the various cytochrome oxidases have evolved by modular evolution, in view of the structure of their electron donor sites. qNOR is further proposed to be the ancestor of all NORs and cytochrome oxidases belonging to the superfamily of haem-copper oxidases.