A unique highly thermostable 2-phosphoglycerate forming glycerate kinase from the hyperthermophilic archaeon Pyrococcus horikoshii: gene cloning, expression and characterization

In Vitro Production of Coenzyme A Using Thermophilic Enzymes

Coenzyme A (CoA) is an essential cofactor present in all domains of life and is involved in numerous metabolic pathways, including fatty acid metabolism, pyruvate oxidation through the tricarboxylic acid (TCA) cycle, and the production of secondary metabolites. This characteristic makes CoA a commercially valuable compound in the pharmaceutical, cosmetic, and clinical industries. However, CoA is difficult to accumulate in living cells at a high level, since it is consumed in multiple metabolic pathways, hampering its manufacturing by typical cell cultivation and extraction approaches. The feedback inhibition by CoA to a biosynthetic enzyme, pantothenate kinase (PanK), is also a serious obstacle for the high-titer production of CoA. To overcome this challenge, in vitro production of CoA, in which the CoA biosynthetic pathway was reconstructed outside cells using recombinant thermophilic enzymes, was performed. The in vitro pathway was designed to be insensitive to the feedback inhibition of CoA using CoA-insensitive type III PanK from the thermophilic bacterium Thermus thermophilus. Furthermore, a statistical approach using design of experiments (DOE) was employed to rationally determine the enzyme loading ratio to maximize the CoA production rate. Consequently, 0.94 mM CoA could be produced from 2 mM d-pantetheine through the designed pathway. We hypothesized that the insufficient conversion yield is attributed to the high K_m value of T. thermophilus PanK toward ATP. Based on these observations, possible CoA regulation mechanisms in T. thermophilus and approaches to improve the feasibility of CoA production through the in vitro pathway have been investigated. IMPORTANCE The biosynthesis of coenzyme A (CoA) in bacteria and eukaryotes is regulated by feedback inhibition targeting type I and type II pantothenate kinase (PanK). Type III PanK is found only in bacteria and is generally insensitive to CoA. Previously, type III PanK from the hyperthermophilic bacterium Thermotoga maritima was shown to defy this typical characteristic and instead shows inhibition toward CoA. In the present study, phylogenetic analysis combined with functional analysis of type III PanK from thermophiles revealed that the CoA-sensitive behavior of type III PanK from T. maritima is uncommon. We cloned type III PanKs from Thermus thermophilus and Geobacillus sp. strain 30 and showed that neither enzyme's activities were inhibited by CoA. Furthermore, we utilized type III PanK for a one-pot cascade reaction to produce CoA.

An online target and rapid screening method for α-glucosidase inhibitors based on capillary electrophoresis

Screening enzymatic active compounds is one of the important fields in drug research. α-Glucosidase can hydrolyze carbohydrates to monosaccharides after meals and lead to the rise of blood glucose levels in human body. Thus, the inhibition of α-glucosidase activity is an effective approach for the diabetes treatment. In this work, we developed a new method to simultaneously screen multiple bioactive compounds within a single CE running. The affect factors on the method performance, including injection, mixing, incubation, separation and detection, were carefully analyzed and discussed. Under the optimum, the mixture consisting of two internal standards (DMSO and 4-nitrophenol) and five compounds (lyoniresinol, hydroxytyrosol, rutin, kaempferol, and quercetin) was simultaneously screened, and kaempferol and quercetin showed stronger activity and this conclusion was also supported by offline assay. Furthermore, molecular docking was employed for investigating its interaction mechanism. Eventually, the established method has been applied to screen potential α-glucosidase inhibitors from an extract of Lycium barbarum and the peak area of rutin, taxifolin, quercetin, and chlorogenic acid in L. barbarum samples changed before and after the enzymatic reaction, confirming that these four compounds had potential inhibitory activities, which was consistent with the literature data. The present work provides a promising method for the target and rapid discovery of bioactive compounds from a plant extract or mixture.

Carbohydrate metabolism in Archaea: current insights into unusual enzymes and pathways and their regulation

The metabolism of Archaea, the third domain of life, resembles in its complexity those of Bacteria and lower Eukarya. However, this metabolic complexity in Archaea is accompanied by the absence of many "classical" pathways, particularly in central carbohydrate metabolism. Instead, Archaea are characterized by the presence of unique, modified variants of classical pathways such as the Embden-Meyerhof-Parnas (EMP) pathway and the Entner-Doudoroff (ED) pathway. The pentose phosphate pathway is only partly present (if at all), and pentose degradation also significantly differs from that known for bacterial model organisms. These modifications are accompanied by the invention of "new," unusual enzymes which cause fundamental consequences for the underlying regulatory principles, and classical allosteric regulation sites well established in Bacteria and Eukarya are lost. The aim of this review is to present the current understanding of central carbohydrate metabolic pathways and their regulation in Archaea. In order to give an overview of their complexity, pathway modifications are discussed with respect to unusual archaeal biocatalysts, their structural and mechanistic characteristics, and their regulatory properties in comparison to their classic counterparts from Bacteria and Eukarya. Furthermore, an overview focusing on hexose metabolic, i.e., glycolytic as well as gluconeogenic, pathways identified in archaeal model organisms is given. Their energy gain is discussed, and new insights into different levels of regulation that have been observed so far, including the transcript and protein levels (e.g., gene regulation, known transcription regulators, and posttranslational modification via reversible protein phosphorylation), are presented.

Molecular characterization of a thermostable aldehyde dehydrogenase (ALDH) from the hyperthermophilic archaeon Sulfolobus tokodaii strain 7

Aldehyde dehydrogenase (ALDH) is a widely distributed enzyme in nature. Although many ALDHs have been reported until now, the detailed enzymatic properties of ALDH from Archaea remain elusive. Herein, we describe the characterization of an ALDH from the hyperthermophilic archaeon Sulfolobus tokodaii. The enzyme (stALDH) could utilize various aldehydes as substrates, and maximal activity was found with acetaldehyde and the coenzyme NAD. The optimal temperature and pH were 80 °C and 8, respectively, and high thermostability was found with the half-life at 90 °C to be 4 h. The enzyme was considerably resistant to nitroglycerin (GTN) inhibition, which could be restored by reducing agent DTT or (±)-α-lipoic acid. Coenzyme NAD or NADP could regulate the enzymatic thermostability, as well as the esterase activity. Molecular modeling suggested that the enzyme harbored similar structural arrangement with its eukaryotic and bacterial counterparts. Sequence alignment showed the conserved catalytic residues E240 and C274 and cofactor interactive sites N142, K165, I168 and E370, the function of which were verified by site-directed mutagenesis analysis. This is the most thermostable ALDH reported until now and the unique property of this enzyme is potentially beneficial in the fields of biotechnology and biomedicine.

A MOFRL family glycerate kinase from the thermophilic crenarchaeon, Sulfolobus tokodaii, with unique enzymatic properties

A glycerate kinase gene (ST2037) from the hyperthermophilic crenarchaeon Sulfolobus tokodaii was cloned and expressed in Escherichia coli. The purified homodimeric protein (45 kDa) specifically catalyzed the formation of 2-phosphoglycerate with D-glycerate as substrate. The thermostable enzyme displayed maximum activity (over 20 min) at 90 degrees C and pH 4.5. The maximal activity was in the presence of Co(2+). The MOFRL family glycerate kinase used AMP as phosphate donor with maximal activity towards GTP. These characteristics of the enzyme suggested its potential in the catalytic production of 2-phosphoglycerate.