Liver Transglutaminase Research Articles

P.26 Liver Transglutaminase 2 Level Comparison Among Different Dietary Interventions

Purpose/Background/ObjectivesTissue transglutaminase (TG2) is a highly expressed protein especially in endothelial cells. TG2 has several functions including transamidation activity which is important in several processes such as extracellular matrix remodeling [1]. TG2 activity takes place in aortic stiffness regulation and atherosclerotic plaque formation [2]. One of the most effective implementation for atheroprone state and general cardiovascular health is calorie restriction (CR). In addition, lipid accumulation and subsequent metabolic disorders can be regulated by CR and longer lifespan can be achieved [3]. In this study we aimed to determine the effect of different CR application types on liver TG2 levels of female mice fed up to 82 weeks old age.MethodsFor this purpose, female MMTV-TGF-a mice fed with different dietary regimes; ad libitum (AL), chronic CR (%15 restriction of AL group), intermittent CR (3 weeks AL (ICR-ReFeed)+1 week %60 restriction of AL (ICR-Restricted), between 10-week to 82-week old. Liver tissue was isolated at 10-week old (AL mice as baseline), 50 and 82 weeks. Then, liver tissue samples were homogenized for western blotting. Analysis made by ImageLab software and Glyceraldehyde-3-Phosphate Dehydrogenase used as housekeeping gene.ResultsTG2 levels were increased in CCR and ICR-R groups, decreased in ICR-RF compared to AL group. In addition, 82-week old AL mice had higher level of TG2 than 10-week old.ConclusionThese results may provide future perspectives about TG2 levels depending on feeding protocols and ageing in kidney. TG2 levels in arteries of the same groups will be examined in further studies.

Purification of bovine liver transglutaminase by gel filtration

Transglutaminases (TGases) are enzymes that catalyze transfer of acyl group and covalent crosslinks formation between peptide-bound glutaminyl residues and amino groups. TGases have many industrial applications and have been purified from various sources. TGase was purified from the bovine liver extract by gel filtration on Sephacryl S-200 HR column. TGase activity was measured using CBZ-l-glutaminylglycine & hydroxylamine and the enzyme was characterized with respect to its response to different temperatures, pHs and salt concentrations. TGase was purified by yield 36.7%, had a weight 74 kDa, a high pH (pH = 8) and temperature (45 °C) optimum. The enzyme was observed to be stable at temperatures below 55 °C and was stable within a narrow pH range of 6.5–8.0. Purified TGase showed Ca2+ dependent characteristics and tended to retain activity at a high NaCl concentration. These results revealed that purified TGase can be used as a potential alternative to other sources.

Specificity of transglutaminase-catalyzed peptide synthesis

Biocatalytic methods for peptide synthesis are of high value due to the rapidly increasing approval of peptide-based therapeutics and the need to develop new analogs. Guinea pig liver transglutaminase (gTG2) catalyzes the cross-linking of peptides and proteins via the formation of γ-glutamyl-ϵ-lysyl isopeptide bonds. In this study, we investigate gTG2-catalyzed peptide bond formation between various amino acid-derived donor and acceptor substrates. Using LC–MS analysis, we demonstrate that gTG2 forms Gly-Xaa and d-Ala-Gly dipeptide products, confirming that its natural transamidation activity can be co-opted for peptide synthesis. An aromatic ester of Gly was the most efficient acyl-donor substrate tested; aromatic esters of d-Ala and l-Ala showed 50-fold lower reactivity or no reactivity, respectively. A computational strategy combining computational protein design algorithms and molecular dynamics simulations was developed to model the binding modes of donor substrates in the gTG2 active site. We show that the inability of gTG2 to efficiently catalyze peptide synthesis from donors containing alanine results from the narrow substrate binding tunnel, which prevents bulkier donors from adopting a catalytically productive binding mode. Our observations pave the way to future protein engineering efforts to expand the substrate scope of gTG2 in peptide synthesis, which may lead to useful biocatalysts for the synthesis of desirable bioactive molecules.

Engineering resonance energy transfer for advanced immunoassays: The case of celiac disease

Celiac disease (CD) is an immune-mediated disorder affecting genetically predisposed subjects. It is caused by the ingestion of wheat gluten and related prolamins. A final diagnosis for this disease can be obtained by examination of jejunal biopsies. Nevertheless, different analytical approaches have been established to detect the presence of anti-tissue transglutaminase antibodies that represent a serological hallmark of the disease. In this work, we explored a new method for the diagnosis of CD based on the detection of serum anti-transglutaminase antibodies by resonance energy transfer (RET) between donor molecules and acceptor molecules. In particular, we labeled the liver transglutaminase (tTG) enzyme from guinea pig and the rabbit anti-tTG antibodies with a couple of fluorescence probes that are able to make RET if they are located within with Förster distance. We labeled tTG with the fluorescence probe DyLight 594 as donor and the anti-tTG antibodies with the fluorescence probe DyLight 649 as acceptor. However, due to the large size of the formed complex (tTG/anti-tTG), and consequently to the low efficiency energy transfer process between the donor–acceptor molecules, we explored a new experimental approach that allows us to extend the utilizable range of RET between donor:acceptor pairs by using one single molecule as donor and multiple molecules as energy acceptors, instead of using a single acceptor molecule as usually occurs in RET experiments. The obtained results clearly show that the use of one donor and multiacceptor strategy enables for a simple and rapid detection of serum anti-transglutaminase antibodies. In addition, our results point out that it is possible to consider this approach as a new method for a wide variety of analytical assays.

Post-translational modification of glutamine and lysine residues of HIV-1 aspartyl protease by transglutaminase increases its catalytic activity

The human immunodeficiency virus type 1 aspartyl protease (HIV-1 PR) is a homodimeric aspartyl endopeptidase that is required for virus replication. HIV-1 PR was shown to act in vitro as acyl-donor and -acceptor for both guinea pig liver transglutaminase (TG, EC 2.3.2.13) and human Factor XIIIa. These preliminary evidences suggested that the HIV-1 PR contains at least three TG-reactive glutaminyl and one lysyl residues. We report here that the incubation of HIV-1 PR with TG increases its catalytic activity. This increase is dependent upon the time of incubation, the concentration of TG and the presence of Ca 2+. Identification of ε-(γ-glutamyl)lysine in the proteolytic digest of the TG-modified HIV-1 PR suggested intramolecular covalent cross-linking of this protease which may promote a non-covalent dimerization and subsequent activation of this enzyme via a conformational change. This hypothesis is supported by the observation that the TG-catalyzed activation of HIV-1 PR was completely abolished by spermidine (SPD) which acts as a competitive inhibitor of ε-(γ-glutamyl)lysine formation. Indeed, in the presence of 1 mM SPD the formation of the isopeptide was decreased of about 80%. The main products of the TG-catalyzed modification of HIV-1 PR in the presence of SPD were N 1- mono(γ-glutamyl)SPD and N 8- mono(γ-glutamyl)SPD. Negligible amount of N 1,N 8- bis(γ-glutamyl)SPD were found. The significance of these results is discussed with respect to the activation of the protease by post-translational modification and design of potential inhibitors.

An in situ and in vitro investigation for the transglutaminase potential in tissue engineering

Transglutaminases (TGases) constitute a family of enzymes that stabilize protein assemblies by gamma-glutamyl-epsilon-lysine crosslinks. The role of tissue transglutaminase (TGase 2) in several pathophysiologies, wound healing applications, biomaterials functionalization, and drug delivery systems provides grounds for its use in tissue engineering. Herein, we initially studied the endogenous TGase activity and expression under normal (skin, duodenum, colon, and small bowel) and pathophysiological (keloid scar) conditions on cadaveric human tissues. Successful inhibition was achieved using low concentrations of BOC-DON-QIV-OMe (0.1 mM and 1 mM for normal skin and keloid scar, respectively), iodoacetamide (0.1 mM and 1 mM for normal skin and keloid scar, respectively), and cystamine dihydrochloride (1 mM and 10 mM for normal skin and keloid scar, respectively), whilst di-BOC-cystamine was found ineffective even at 100 mM concentration. Secondly, the addition of exogenous guinea pig liver transglutaminase (gpTGase) onto the inhibited tissues and collagen scaffolds was studied, and results presented advocate its use as potential tissue adhesive and drug delivery tool. However, the investigation of its crosslinking extent using second harmonic generation microscopy and differentially scanning calorimetry revealed rather poor stabilization function. Overall, our study indicates that TGase 2 has a role as a biological glue to consolidate various micro-structural components of tissues and biomaterials.

Photolabeling of Tissue Transglutaminase Reveals the Binding Mode of Potent Cinnamoyl Inhibitors

We have recently developed a new class of cinnamoyl derivatives as potent tissue transglutaminase (TG2) inhibitors. Herein, we report the synthesis of a diazirine derivative of these inhibitors and its application to the photolabeling of its binding site on guinea pig liver transglutaminase. Two novel homology models were generated for this commonly studied TG2, which differ in the conformational state they represent. Tryptic digest and mass spectrometric analysis of the photolabeling experiment showed that only residue Cys230 was labeled, and our homology models were used to visualize these results. This visualization suggested that Cys230 is somewhat more solvent-exposed in the "closed" conformation of TG2, compared to the "open" conformation. Docking experiments suggested binding modes consistent with the labeling pattern that would block access to the tunnel leading to the active site, consistent with the observed mode of inhibition. However, while these modeling simulations favored the closed conformation as the target of our cinnamoyl inhibitors, native PAGE experiments indicated the open conformation of the enzyme in fact predominates in the presence of our photolabeling derivative. These results are important for understanding the binding modes of TG2 inhibitors in general and will be critical for the structure-based design of future inhibitors.

Development of an isoenzyme-specific colorimetric assay for tissue transglutaminase 2 cross-linking activity

Tissue transglutaminase (TGase 2) belongs to the multigene transglutaminase family of Ca 2+-dependent protein cross-linking enzymes. Based on the transamidation activity of TGase 2, a novel colorimetric assay has been developed using covalently coupled spermine to carboxy-substituted polystyrene plates and biotinylated pepT26, an excellent acyl-donor substrate, highly specific for TGase 2. The assay is based on the incorporation of the gamma-carboxamide of glutamine of pepT26 into the immobilized spermine. The amount of biotinylated pepT26 bound to the plate, as measured by the activity of streptavidin-peroxidase, is directly proportional to the TGase activity. The colorimetric procedure showed a good correlation ( r = 0.995) with the commonly used radiometric filter paper method for TGase2, and provides linear dose–response curves over a wide range of hrTGase2 concentrations (2.5–40 μU/ml). In addition, the assay shows higher sensitivity when compared with our previous TG-colorimetric test (more than 50-fold increase) and other existing assays. PepT26 displays strong reactivity with TGase 2, and no reactivity with TGases 1, 3, and FXIII. The procedure constitutes a rapid, TG2-specific, sensitive, and nonisotopic method for the measurement of TGase 2 activity in as low as 4 ng of hrTGase 2 and purified guinea pig liver transglutaminase, and 1.25 μg of guinea pig liver extracts.

Identification of glutaminyl sites on β-lactoglobulin for threadfin bream liver and microbial transglutaminase activity by MALDI-TOF mass spectrometry

The cross-linking of β-lactoglobulin (BLG) was efficiently catalysed by microbial transglutaminase (MTG) but not by fish (threadfin bream) liver transglutaminase (FTG). BLG cross-linking was inhibited by 2 mM 5-(biotinamido) pentylamine (BPNH 2) and MTG incorporated BPNH 2 into BLG ∼5 times more than was FTG. The glutaminyl sites for the incorporation of BPNH 2 into BLG by FTG and MTG were identified using matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS). MALDI-TOF MS analyses showed that MTG and FTG incorporated 4 and 1 residues of BPNH 2 per molecule of BLG, respectively. The BPNH 2-tagged BLG was digested by trypsin and BPNH 2-tagged peptides were selectively purified by avidin-affinity chromatography. Amino acid sequences of BPNH 2-tagged peptides were identified by comparing their MALDI-TOF mass spectra with the theoretical mass profiles from the MASCOT database. The BPNH 2-modification sites catalysed by MTG were glutamine (Q)13, Q68, Q15 or Q20, Q155 or Q159, whilst FTG only incorporated BPNH 2 into BLG at Q68. The different reactivities between FTG and MTG might be due to the different accessibilities of these TGases to the Q residues as well as to differences in substrate specificities.

Reversible and Competitive Cinnamoyl Triazole Inhibitors of Tissue Transglutaminase

A series of 15 cinnamoyl triazole derivatives was prepared by Cu(I)-catalyzed azide/alkyne [3+2]-cycloaddition reactions and examined as inhibitors of guinea-pig liver transglutaminase. Several compounds exhibited activity as reversible inhibitors that were competitive with acyl donor transglutaminase substrates. For example, triazole 4d has a K(i) value of 174 nM and represents one of the most potent reversible transglutaminase inhibitors reported to date.

Reactivity of Fish and Microbial Transglutaminases on Glutaminyl Sites of Peptides Derived from Threadfin Bream Myosin

Fish liver transglutaminase (FTG), a Ca(2+)-dependent enzyme, exhibits different characteristics from the Ca(2+)-independent microbial transglutaminase (MTG), leading to potential differences in their substrate specificity and reactivity. The ability of these enzymes to catalyze isopeptide bond formation by incorporating 5-(biotinamido)pentylamine (BPNH2) into peptides derived by tryptic digestion of threadfin bream (TB)-myosin was investigated to identify reaction sites and substrate specificity using a peptidomic strategy. BPNH2 was incorporated into TB-myosin peptides to a greater extent by MTG than FTG. Peptides derived from TB-myosin heavy chain (MHC) shared highest similarity to amberjack-MHC on the basis of a Mascot database search. Amino acid sequences and modification sites of BPNH2-tagged peptides were identified by tandem mass spectrometry based on the amberjack-MHC sequence. The BPNH2 modification sites catalyzed by both TGases were at the myosin rod. Most of the BPNH2 peptides contained charged amino acids (E, R, K) at the glutaminylamide site of reactive glutamine (Q*). The alpha-acrylamide site of Q* contained E, F, or L on peptides catalyzed by both enzymes, I, Q, or A on peptides catalyzed only by FTG, and V on a peptide catalyzed only by MTG. These results demonstrate the different structural requirements for glutaminyl substrates between these two enzymes.

Identification of Factor-XIIIa-Reactive Glutaminyl Residues in the Propolypeptide of Bovine von Willebrand Factor

von Willebrand factor is a large multimeric plasma protein which plays important roles in platelet aggregation, blood coagulation and probably also in the adhesion of endothelial cells. A 100-kDa propeptide, called the propolypeptide of von Willebrand factor (pp-vWF), is generated during biosynthesis. We found that pp-vWF served as a substrate for transglutaminases including human factor XIIIa and guinea pig liver transglutaminase [Usui, T., Takagi, J. & Saito, Y. (1993) J. Biol. Chem. 268, 12311–123161. As such, it could form cross-linked copolymers with the extracellular matrix protein, laminin, making it all the more likely that pp-vWF plays a role in cell adhesion phenomena [Takagi, J., Sudo, Y., Saito, T. & Saito, Y. (1994) Eur. J. Biochem. 222, 861–867]. In this work, we identified the Gln residues in pp-vWF specifically reacting with blood coagulation factor XIIIa as amine acceptors. The fluorescent amine, dansylcadaverine, was employed for labeling the enzyme-reactive sites of the protein. Following partial proteolysis, fragments containing the labeled Gln residues were isolated by passage through an anti-dansyl affinity chromatographic column. Amino acid sequence analyses of the fragments revealed that, out of about 40 Gln residues in pp-vWF, only four could be modified in the factor-XIIIa-catalyzed reaction.

Cinnamoyl Inhibitors of Tissue Transglutaminase

Transglutaminases (TGases) catalyze the intermolecular cross-linking of certain proteins and tissue TGases (TG2) are involved in diverse biological processes. Unregulated, high TGase activities have been implicated in several physiological disorders, but few reversible inhibitors of TG2 have been reported. Herein, we report the synthesis of a series of novel trans-cinammoyl derivatives, discovered to be potent inhibitors of guinea pig liver transglutaminase. The most effective inhibitors evaluated can be sorted into two subclasses: substituted cinnamoyl benzotriazolyl amides and the 3-(substituted cinnamoyl)pyridines, referred to more commonly as azachalcones. Kinetic evaluation of both of these subclasses revealed that they display reversible inhibition and are competitive with acyl donor TGase substrates at IC50 values as low as 18 microM. An analysis of structure-activity relationships within these series of inhibitors permitted the identification of potentially important binding interactions. Further testing of some of the most potent inhibitors demonstrated their selectivity for TG2 and their potential for further development.

PARTIAL PURIFICATION AND CHARACTERIZATION OF TRANSGLUTAMINASE FROM THREADFIN BREAM (NEMIPTERUS SP.) LIVER

Transglutaminase (TGase) from the threadfin bream ([TB]Nemipterus sp.) liver was partially purified using ion exchange, size exclusion and affinity chromatography. Three protein bands with molecular weight (Mw) of 95, 63 and 43 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were observed. Only one distinct fluorescent band appeared on the TGase activity staining of the native-PAGE. When the protein band was eluted and analyzed on the SDS-PAGE, it showed a single band with an Mw of 95 kDa. The enzyme required Ca2+up to 1 mM for full activation. TGase was also activated by 10 mM Sr2+. Dithiothreitol had no effect on activity. TGase activity was unaffected by NaCl up to 0.6 M and reduced to 75% at 1.2 M NaCl. Optimum pH and temperature was 8.5–9.0 and 50C, respectively. TGase activity was markedly inhibited by the sulfhydryl reagents. The enzyme catalyzed the cross-linking of the TB myosin heavy chains. PRACTICAL APPLICATIONS Threadfin bream (TB) liver transglutaminase (TGase) exhibited Ca2+-dependent characteristic similar to muscle TGase. The enzyme catalyzed the cross-linking of myosin, and therefore, could be applied to improve the textural properties of muscle proteins. The enzyme remained its high activity up to 1.2 M NaCl (≈7% w/v), indicating its potential application in foods containing a relatively high NaCl. The biochemical characteristics of the TB liver TGase are critical information leading to more understanding in the nature of the enzyme as well as determining the optimum conditions for food applications. Moreover, the presented purification scheme could be adopted to recover TGase from the TB liver, which is currently a solid waste of the surimi industry.

Transglutaminase Participates in UVB-Induced Cell Death Pathways in Human Corneal Epithelial Cells

Ultraviolet light (UVB) is known to cause apoptosis in human corneal epithelial cells. This study evaluates the role of transglutaminase in regulating tumor necrosis factor (TNF) receptor clustering as well as caspase activation in UVB-induced apoptosis in human corneal epithelial cells. A human corneal epithelial cell line was used. A single dose of UVB (20 mJ/cm2) was used as a stimulus. Cell viability and cell death were investigated by MTT, terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL), and caspase-3 assays. Immunofluorescent staining was used to investigate TNF receptor-I clustering at various time intervals after UVB. Short interfering RNA was used to knock down transglutaminase-2 expression. Fluorescein-cadaverine uptake was used to assess transglutaminase activity. A noncovalent peptide delivery system was used to transfect guinea pig liver transglutaminase into corneal epithelial cells. UVB increased transglutaminase activity, reduced cell viability, and increased TUNEL staining. UVB or TNF-alpha promoted TNF-receptor-I clustering, a process inhibited by the transglutaminase inhibitor, mono-dansyl cadaverine. UVB also increased activated caspase-3, in a manner suppressible by mono-dansyl cadaverine. Intracellular delivery of exogenous transglutaminase markedly increase caspase-3 activation compared with the vehicle control. Transglutaminase enzymatic activity is involved in corneal epithelial cell death after UVB and appears to participate in two steps regulating this process, clustering of TNF receptor-I and caspase-3 activation.

A Rapid Transglutaminase Assay for High-Throughput Screening Applications

Transglutaminases (TGs) are widely distributed enzymes that catalyze posttranslational modification of proteins by Ca(2+)-dependent cross-linking reactions. The family members of TGs participate in many significant processes of biological functions such as tissue regeneration, cell differentiation, apoptosis, and certain pathologies. A novel technique for TG activity assay was developed in this study. It was based on the rapid capturing, fluorescence quenching, and fast separation of the unreacted fluorescent molecules from the macromolecular product with magnetic dextran-coated charcoal. As few as 3 ng of guinea pig liver transglutaminase (gpTG) could be detected by the method; activities of 96 TG samples could be measured within an hour. The K(m) of gpTG determined by this method for monodansylcadaverine (dansyl-CAD) and N, N-dimethylcasein was 14 and 5 muM, respectively. A typical competitive inhibition pattern of cystamine on dansyl-CAD for gpTG activity was also demonstrated. The application of this technique is not limited to the use of dansyl-CAD as the fluorescent substrate of TG; other small fluor-labeled TG substrates may substitute dansyl-CAD. Finally, this method is rapid, highly sensitive, and inexpensive. It is suitable not only for high-throughput screening of enzymes or enzyme inhibitors but also for enzyme kinetic analysis.

In vitro modification of betaine-homocysteine S-methyltransferase by tissue-type transglutaminase

Transglutaminases catalyze the cross-linking and amine incorporation of proteins, and are implicated in various biological phenomena. To elucidate the physiological roles of transglutaminase at the molecular level, we need to identify its physiological protein substrates and clarify the relationship between transglutaminase modification of protein substrates and biological responses. Here we examined whether betaine-homocysteine S-methyltransferase (BHMT: EC 2.1.1.5) can be a substrate of tissue-type transglutaminase by in vitro experiments using porcine liver BHMT and guinea pig liver transglutarninase. Guinea pig liver transglutaminase incorporated 5-(biotinamido) pentylamine and [ 3 H] histamine into BHMT in a time-dependent manner. Putrescine and spermidine also seemed to be incorporated into BHMT by transglutaminase. In the absence of the primary amines, BHMT subunits were cross-linked intra- and intermolecularly. BHMT activity was decreased significantly through the cross-linking by transglutaminase. Histamine incorporation slightly reduced the BHMT activity. Peptide fragments of BHMT containing the glutamine residues reactive for transglutaminase reaction were isolated through biotin labelling, proteinase digestion, biotin-avidin a affinity separation, and reverse phase HPLC. The results of amino acid sequence analyses of these peptides and sequence homology alignment with other mammalian liver BHMT subunits showed that these reactive glutamine residues were located in the region near the carboxyl terminal of porcine BHMT subunit. These results suggested that the liver BHMT can be modified by tissue-type transglutaminase and its activity is regulated repressively by the modification, especially by the cross-linking. This regulatory reaction might be involved in the regulation of homocysteine metabolism in the liver.

Serotonylation Activates Platelets

Platelets, small anuclear cellular fragments in the circulation, are essential to the clotting process and are implicated in vascular disorders such as thrombosis and atherosclerosis. Platelets adhere to sites of damaged vascular endothelia through a process involving von Willebrand factor (vWF). When stimulated, platelets also release granules that contain various proaggretory factors such as adenosine diphosphate, adenosine triphosphate, serotonin (5-HT), calcium, and multimeric forms of vWF. Platelets also have 5-HT receptors and 5-HT reuptake transporters (SERTs). Using a tryptophan hydroxylase 1 knockout mouse (Tph is the rate-limiting enzyme in 5-HT biosynthesis, and Tph1 is the peripheral isoform), Walther et al . analyzed the role of 5-HT in platelet aggregation and degranulation. Clotting times were prolonged in the Tph1 –/– mice, and the mice were protected from thrombotic vessel occlusion, which suggests a defect in platelet aggregation. Using pharmacological inhibitors of the plasma membrane SERT and the vesicular monoamine transporter, the authors demonstrated that cytosolic 5-HT was essential for effective aggregation of isolated platelets. Platelets treated with radioactive 5-HT showed a pool of unreleasable 5-HT in the aggregated platelets. Secretion of granule contents (vWF) was stimulated in permeabilized platelets from the Tph1 –/– mice by the addition of 5-HT, transglutaminase (TG), and skeletal muscle cytosol. Analysis of the proteins isolated from aggregated platelets showed multiple bands labeled with [ 14 C]5-HT, including the guanosine triphosphatase (GTPase) RhoA. In vitro, Rab4, which controls granule secretion in platelets, was also transamidated by purified liver TGs. Thus, the authors propose that 5-HT stimulates an increase in calcium through its activation of its G q -coupled receptor. The calcium stimulates the activity of TGs, which use 5-HT taken up by the SERT to transamidate GTPases, which renders them constitutively active, promoting changes in platelet shape (RhoA) and degranulation (Rab4). This ultimately produces irreversible platelet aggregation. D. J. Walther, J.-U. Peter, S. Winter, M. Höltje, N. Paulmann, M. Grohmann, J. Vowinckel, V. Alamo-Bethencourt, C. S. Wilhelm, G. Ahnert-Hilger, M. Bader, Serotonylation of small GTPases is a signal transduction pathway that triggers platelet α-granule release. Cell 115 , 851-862 (2003). [Online Journal]

Expression and rapid purification of highly active hexahistidine-tagged guinea pig liver transglutaminase

Tissue transglutaminase has been identified as a contributor to a wide variety of diseases, including cataract formation and Celiac disease. Guinea pig tissue transglutaminase has a very broad substrate specificity and therefore is useful for kinetic studies using substrate analogues. Here, we report the expression in Escherichia coli of a hexahistidine-tagged guinea pig liver tissue transglutaminase (His 6-tTGase) allowing rapid purification by immobilized-metal affinity chromatography. Using this procedure we have obtained the highest reported specific activity (17 U/mg) combined with a high yield (22 mg/L of culture) for recombinant TGase using a single-step purification protocol. Using two independent spectrophotometric assays, we determined that the K m value of the recombinant enzyme with the substrate Cbz–Gln–Gly is in the same range as values reported in the literature for the native enzyme. We have thus developed a rapid and reproducible protocol for the preparation of high quality tissue TGase.

Application of transglutaminases in the modification of wool textiles

The use of the protein-crosslinking enzymes transglutaminases (EC 2.3.2.13), as biocatalysts in the processing of wool textiles offers a variety of exciting and realistic possibilities, which include reducing the propensity of wool fabric to shrink and maintaining or increasing fabric strength. Guinea pig liver (GPL) transglutaminase or the microbial transglutaminase isolated from Streptoverticilium mobaraense, when applied to wool either alone or following a protease treatment, resulted in an increase in wool yarn and fabric strength (up to a 25% increase compared to a control). This indicates that transglutaminases can remediate the negative effects of proteolytic treatments in terms of loss in fibre strength. Incubation of samples pretreated with different oxidative and reducing agents with both sources of transglutaminases led to significant increases in tensile strength for all samples tested, suggesting that yarn strength lost following chemical treatments can also be recovered. The two different transglutaminases (TGases) could also impart a significant reduction in fabric shrinkage. The incorporation of primary amine transglutaminase substrates into wool fibres, with a view to altering wool functionality, was demonstrated using the incorporation of the fluorescent primary amine fluorescein cadaverine (FC). Incubation of wool with this fluorescent amine and transglutaminase led to high levels of incorporation into the fibres. The treatment of wool textiles with transglutaminases indicates that a number of novel and radically different finishes for wool textiles can be developed.