A kinetic study of thioredoxin-glutathione reductase (TGR) from Taenia crassiceps metacestode (cysticerci) was carried out. The results obtained from both initial velocity and product inhibition experiments suggest the enzyme follows a two-site ping-pong bi bi kinetic mechanism, in which both substrates and products are bound in rapid equilibrium fashion. The substrate GSSG exerts inhibition at moderate or high concentrations, which is concomitant with the observation of hysteretic-like progress curves. The effect of NADPH on the apparent hysteretic behavior of TGR was also studied. At low concentrations of NADPH in the presence of moderate concentrations of GSSG, atypical time progress curves were observed, consisting of an initial burst-like stage, followed by a lag whose amplitude and duration depended on the concentration of both NADPH and GSSG. Based on all the kinetic and structural evidence available on TGR, a mechanism-based model was developed. The model assumes a noncompetitive mode of inhibition by GSSG in which the disulfide behaves as an affinity label-like reagent through its binding and reduction at an alternative site, leading the enzyme into an inactive state. The critical points of the model are the persistence of residual GSSG reductase activity in the inhibited GSSG-enzyme complexes and the regeneration of the active form of the enzyme by GSH. Hence, the hysteretic-like progress curves of GSSG reduction by TGR are the result of a continuous competition between GSH and GSSG for driving the enzyme into active or inactive states, respectively. By using an arbitrary but consistent set of rate constants, the experimental full progress curves were successfully reproduced in silico.

Juan L. Rend&#xf3;n

Mauricio Miranda-Leyva

Alberto Guevara-Flores

Jos&#xe9; de Jes&#xfa;s Mart&#xed;nez-Gonz&#xe1;lez

Irene Patricia del Arenal

Oscar Flores-Herrera

Juan P. Pardo

Insight into the Mechanistic Basis of the Hysteretic-Like Kinetic Behavior of Thioredoxin-Glutathione Reductase (TGR)

Phospholipase A2 (PLA2) is a secretory digestive enzyme that hydrolyzes ester bond at sn-2 position of dietary phospholipids, creating free fatty acid and lysophospholipid. The free fatty acids (arachidonic acid) are absorbed into midgut cells. Aedes albopictus and Culex quinquefasciatus digestive PLA2 was characterized using a microplate PLA2 assay. The enzyme showed substantial activities at 6 and 8&#x2009;&#x3bc;g/&#x3bc;l of protein concentration with optimal activity at 20 and 25&#x2009;&#x3bc;g/&#x3bc;l of substrate concentration in Aedes albopictus and Culex quinquefasciatus, respectively. PLA2 activity from both mosquitoes increased in a linear function up to 1 hour of the reaction time. Both enzymes were sensitive to pH and temperature. PLA2 showed higher enzyme activities in pH 8.0 and pH 9.0 from Aedes albopictus and Culex quinquefasciatus, respectively, at 40&#xb0;C of incubation. The PLA2 activity decreased in the presence of 5&#x2009;mM (Aedes albopictus) and 0.5&#x2009;mM (Culex quinquefasciatus) site specific PLA2 inhibitor, oleyloxyethylphosphorylcholine. Based on the migration pattern of the partially purified PLA2 on SDS-PAGE, the protein mass of PLA2 is approximately 20&#x2013;25&#x2009;kDa for both mosquitoes. The information on PLA2 properties derived from this study may facilitate in devising mosquitoes control strategies especially in the development of inhibitors targeting the enzyme active site.

Nor Aliza Abdul Rahim

Marlini Othman

Muna Sabri

David W. Stanley

A Midgut Digestive Phospholipase A2 in Larval Mosquitoes, Aedes albopictus and Culex quinquefasciatus

Enzymatic hydrolysis is an important but expensive step in the process to obtain enzyme derived products. Thus, the production of efficient enzymes is of great interest for this biotechnological application. The production of xylanase by Aspergillus foetidus in soybean residues was optimized using <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" width="16.776pt" style="vertical-align:-0.3499002pt" id="M1" height="11.9413pt" version="1.1" viewBox="-0.0498162 -11.5914 16.776 11.9413"><g transform="matrix(.013,0,0,-0.013,0,0)"><path id="g113-51" d="M412 140C382 77 369 73 315 73H129L270 222C362 320 402 379 402 466C402 571 322 635 234 635C177 635 130 609 99 576L42 495L64 475C90 514 133 568 201 568C274 568 318 519 318 435C318 349 255 267 193 193C144 135 87 78 32 23V0H405C417 45 427 89 440 131L412 140Z"/></g><g transform="matrix(.013,0,0,-0.013,9.145,0)"><path id="g117-42" d="M528 54L331 254L528 455L492 493L294 291L96 493L60 455L257 254L60 54L96 16L294 217L492 16L528 54Z"/></g></svg><svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" width="11.361pt" style="vertical-align:-0.3499002pt" height="11.9413pt" version="1.1" viewBox="19.6321838 -11.5914 11.361 11.9413"><g transform="matrix(.013,0,0,-0.013,19.682,0)"><use xlink:href="#g113-51"/></g><g transform="matrix(.0091,0,0,-0.0091,25.922,-5.741)"><path id="g50-52" d="M290 377C321 398 342 415 358 430C378 450 389 473 389 502C389 578 329 635 238 635H237C184 635 137 610 109 578L64 515L88 493C112 529 154 573 208 573S303 542 303 482C303 409 233 370 141 341L149 308C165 313 190 319 215 319C272 319 341 283 341 193C342 98 292 43 222 43C163 43 122 72 96 94C88 101 79 100 70 94C61 87 47 73 46 60C44 47 48 37 62 23C76 10 118 -12 165 -12C238 -12 430 62 430 223C430 297 379 359 290 375V377Z"/></g></svg> factorial designs. The experimental data was fitted into a polynomial model for xylanase activity. Statistical analyses of the results showed that variables pH and the interaction of pH and temperature had influenced the production of xylanase, with the best xylanase production level (13.98 U/mL) occurring at fermentation for 168 hours, pH 7.0, 28°C, and 120 rpm.

Luana Cunha

Raquel Martarello

Paula Monteiro de Souza

Marcela Medeiros de Freitas

Kleber Vanio Gomes Barros

Edivaldo Ximenes Ferreira Filho

Mauricio Homem-de-Mello

P&#xe9;rola Oliveira Magalh&#xe3;es

Optimization of Xylanase Production from Aspergillus foetidus in Soybean Residue

Pectinase is one of the important enzymes of industrial sectors. Presently, most of the pectinases are of plant origin but there are only a few reports on bacterial pectinases. The aim of the present study was to isolate a novel and potential pectinase producing bacterium as well as optimization of its various parameters for maximum enzyme production. A total of forty bacterial isolates were isolated from vegetable dump waste soil using standard plate count methods. Primary screening was done by hydrolysis of pectin. Pectinase activity was determined by measuring the increase in reducing sugar formed by the enzymatic hydrolysis of pectin. Among the bacterial isolates, the isolate K6 exhibited higher pectinase activity in broth medium and was selected for further studies. The selected bacterial isolate K6 was identified as Chryseobacterium indologenes strain SD. The isolate was found to produce maximum pectinase at 37&#xb0;C with pH 7.5 upon incubation for 72 hours, while cultured in production medium containing citrus pectin and yeast extract as C and N sources, respectively. During enzyme-substrate reaction phase, the enzyme exhibited its best activity at pH of 8.0 and temperature of 40&#xb0;C using citrus pectin as substrate. The pectinase of the isolate showed potentiality on different types of fruit juice clarification.

Karabi Roy

Sujan Dey

Md. Kamal Uddin

Rasel Barua

Md. Towhid Hossain

Extracellular Pectinase from a Novel Bacterium Chryseobacterium indologenes Strain SD and Its Application in Fruit Juice Clarification

Phytase plays a prominent role in monogastric animal nutrition due to its ability to improve phytic acid digestion in the gastrointestinal tract, releasing phosphorus and other micronutrients that are important for animal development. Moreover, phytase decreases the amounts of phytic acid and phosphate excreted in feces. Bioinformatics approaches can contribute to the understanding of the catalytic structure of phytase. Analysis of the catalytic structure can reveal enzymatic stability and the polarization and hydrophobicity of amino acids. One important aspect of this type of analysis is the estimation of the number of &#x3b2;-sheets and &#x3b1;-helices in the enzymatic structure. Fermentative processes or genetic engineering methods are employed for phytase production in transgenic plants or microorganisms. To this end, phytase genes are inserted in transgenic crops to improve the bioavailability of phosphorus. This promising technology aims to improve agricultural efficiency and productivity. Thus, the aim of this review is to present the characterization of the catalytic structure of plant and microbial phytases, phytase genes used in transgenic plants and microorganisms, and their biotechnological applications in animal nutrition, which do not impact negatively on environmental degradation.

Alex Sander Rodrigues Cangussu

Deborah Aires Almeida

Raimundo Wagner de Souza Aguiar

Sidnei Emilio Bordignon-Junior

Kelvinson Fernandes Viana

Luiz Carlos Bertucci Barbosa

Edson Wagner da Silva Cangussu

Igor Viana Brandi

Augustus Caeser Franke Portella

Gil Rodrigues dos Santos

Eliane Macedo Sobrinho

William James Nogueira Lima

Characterization of the Catalytic Structure of Plant Phytase, Protein Tyrosine Phosphatase-Like Phytase, and Histidine Acid Phytases and Their Biotechnological Applications

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Enzyme Research publishes original research articles as well as review articles that advance our understanding of enzymes and the way in which they work, both in vivo and in vitro.

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Enzyme Research ceased publication in 2019 and is no longer accepting submissions.

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Enzyme Research publishes original research articles as well as review articles that advance our understanding of enzymes and the way in which they work, both in vivo and in vitro.

Enzyme Research