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H Gehring

Publications and source records attributed to H Gehring.

At least 19 recordsLinked to original sources
PubMed2006

Electrical impedance tomography: changes in distribution of pulmonary ventilation during laparoscopic surgery in a porcine model.

BACKGROUND: Because of the creation of a pneumoperitoneum, impairment of ventilation is a common side-effect during laparoscopic surgery. Electrical impedance tomography (EIT) is a method with the potential for becoming a tool to quantify these alterations during surgery. We have studied the change of regional ventilation during and after laparoscopic surgery with EIT and compared the diagnostic findings with computed tomography (CT) scans in a porcine study. MATERIALS AND METHODS: After approval by the local animal ethics committee, six pigs were included in the study. Two laparoscopic operations were performed [colon resection (n=3) and fundoplicatio (n=3)]. The EIT measurements (6th parasternal intercostal space) were continuously recorded by an EIT prototype (EIT Evaluation Kit, Dräger Medical, Lübeck, Germany). To verify ventilatory alterations detected by EIT, a CT scan was performed postoperatively. RESULTS: Ventilation with defined tidal volumes was significantly correlated to EIT measurements (r2=0.99). After creation of the pneumoperitoneum, lung compliance typically decreased, which agreed well with an alteration of the distribution of pulmonary ventilation measured by EIT. Elevation of positive end-inspiratory pressure reopened non-aerated lung areas and showed a recovery of the regional ventilation measured by EIT. Additionally, we could detect pulmonary complications by EIT monitoring as verified by CT scans postoperatively. CONCLUSION: EIT monitoring can be used as a continuous non-invasive intraoperative monitor of ventilation to detect regional changes of ventilation and pulmonary complications during laparoscopic surgery. These EIT findings indicate that surgeons and anesthetists may eventually be able to optimize ventilation directly in the operating theatre.

Animals↗
PubMed2005

[Unclear intraoperative cardiorespiratory decompensation. Anaphylactic reaction?].

During anaesthesia a patient is exposed to a variety of substances, all of which could lead to anaphylactic reactions. In addition, other drugs may exert clinical side-effects by non-immunological mechanisms, e.g. by direct stimulation of the release of histamine by mast cells. Initially, the observed symptoms, such as hypotension or tachycardia, may be misunderstood by the anaesthetist, leading to a possible delay in diagnosis and subsequent treatment of the anaphylactic event. Cardiac ischemia and lung embolisms are important differential diagnoses that often cannot be definitely ruled out during the acute situation and that have to be followed up once the patient has been stabilised. We report a case of anaphylactic reaction after the administration of ampicillin which required treatment and ventilation in the intensive care unit. Despite an accurate determination of serum tryptase levels, the diagnosis of an anaphylactic reaction to ampicillin was eventually confirmed by skin testing. During anaesthesia, anaesthetists should consider anaphylaxis when unforeseen symptoms such as bronchospasm, haemodynamical instability and/or flush arise. In cases of unexpected reactions, patients should undergo allergological follow-up to prevent fatal re-exposure.

Aged↗
PubMed2002

Immunophilins and HIV-1 infection.

Peptides of the V3 loop of the HIV-1 envelope glycoprotein gp120 have been shown to bind with high affinity to the immunophilins cyclophilin (Cyp) A, CypB and the FK506-binding protein 12 (FKBP12) [10]. We investigated whether immunophilins affect HIV-1 infection by assuming they are able to bind to the V3 loop of gp120. T cells and peripheral blood mononuclear cells were infected with T-cell-tropic or macrophage-tropic HIV-1 strains, respectively, in the presence of different concentrations of immunophilins. P24 antigen ELISA and real-time PCR measurements demonstrated that exogenously added immunophilins do not influence HIV-1 infection. CypA is known to interact with the HIV-1 Gag polyprotein and to be incorporated into the virions. This incorporation can be prevented by cyclosporin A (CsA) resulting in a decreased yield of infectious virus, the mechanism of which is unknown. We measured a normal production of proviral DNA in the first round of infection in CsA treated cells but afterwards, infection was decreased if CsA was present. Pre-treatment of the HIV-1 inocula with CsA, blocking the function of virus-associated CypA, did not inhibit the ensuing yield of infection. We therefore may conclude that endogenous CypA exerts its action after reverse transcription but before virus maturation, probably during capsid formation. FK520, an immunosuppressor which binds to FKBP, had no effect on HIV-1 infection.

Cyclophilin A↗
PubMed2002

Development and evaluation of a video program for presentation prior to elective cardiac surgery.

BACKGROUND: : The objective of the present study was to develop and evaluate the effects of a preparatory videotape on endocrine stress responses of patients prior to cardiac surgery and to analyze patient acceptance of this video for preoperative preparation. METHODS: : 101 male patients prior to elective cardiac surgery were enrolled into the study. On the day before surgery, patients were assigned to one of the following groups: group 1 (n = 51) saw a video with realistic information about the upcoming perioperative procedure, and group 2 (n = 50) saw a video of the same length without surgery-related information. Venous blood was sampled before and 15 min after the video presentation. On the second postoperative day, patients filled in a questionnaire concerning their experiences of having preoperatively watched the video. RESULTS: : After viewing the video, blood levels of cortisol, adrenocorticotropic hormone (ACTH), beta-endorphin, prolactin, epinephrine and norepinephrine in patients of group 1 were not significantly different compared to values measured before the video presentation. In patients of group 2, blood levels of cortisol, ACTH, prolactin and norepinephrine were significantly lower after video presentation compared to values obtained before the video. Patients of group 1 (compared to group 2) were significantly more often of the opinion that the video had helped in the preparation for surgery, and that they would like to repeat this adjunct preoperative video preparation in another similar situation. CONCLUSION: : We conclude from our results that (i); cardiac surgical patients prefer preoperatively an adjunct surgery-related video preparation to a non-specific video presentation, and that (ii); preoperative preparation with realistic information about the upcoming medical procedure in patients undergoing cardiac surgery does not lead to an increase in endocrine stress hormone levels.

Aged↗
PubMed2002

Accuracy of point-of-care-testing (POCT) for determining hemoglobin concentrations.

BACKGROUND: While point-of-care testing (POCT) is being used increasingly as a basis for deciding on perioperative erythrocyte transfusion, no valid standards currently exist concerning the accuracy of Hb concentration measurements. For clinical employment, however, the confidence limits (+/-2 SD) of these measurements should lie close to 5 g/l. The aim of the present study was to evaluate the accuracy and precision of point-of-care testing for blood hemoglobin concentration (cHb in g/l) measurements in critically ill patients. METHODS: Fifty blood samples from 50 postoperative patients requiring intensive care treatment were withdrawn from a cannula in the radial artery into a 2-ml heparinized syringe (containing wet sodium heparinate in the conus), in a 2-ml Monovette with 50 IE lithium heparinate, and into a 2.7-ml cuvette with 1.6 mg potassium EDTA/ml blood. The POCT battery consisted of two blood gas analyzers (ABLTM 625 and 725, Radiometer, Copenhagen), the HemoCue system (Mallinckrodt Medical, Germany), and an automated hematology analyzer (M-2000(R), Sysmex, Germany). The cyanmethemoglobin method served as the reference 'gold standard' procedure. The blood gas analyzer and HemoCue systems were tested using dry and wet heparinized blood samples. RESULTS: Hemoglobin concentrations of the reference measurements ranged from 73.9 to 159.4 g/l. The automated hematology analyzer method did reveal a small but systematic deviation for higher cHb values. For the blood gas analyzer and HemoCue system procedures there was no systematic deviation of bias for either the first measurement or the averaged data. Bland & Altman analysis revealed a larger scattering for the wet heparinized samples. CONCLUSIONS: The above-stated requirement for POCT systems, i.e. that the confidence limits should lie close to 5 g/l cHb, held true for the dry heparinized samples of the blood gas analyzer (1st measurement and mean of 2), the HemoCue system (mean of 3) and the automated hematology analyzer.

Blood Gas Analysis↗
PubMed2002

Detecting and quantifying absorbed irrigation fluid by measuring mannitol and sorbitol concentrations in serum samples, and by ethanol monitoring.

OBJECTIVE: To describe a modified and improved technique which, in one measurement, estimates the influx of irrigation fluid during endoscopic endometrial ablation or prostate resection, and provides both rapid confirmation of the diagnosis and an estimate of the amount of fluid absorbed by detecting markers which pass from the irrigation fluid to the serum, i.e. mannitol or sorbitol. PATIENTS AND METHODS: Control samples were taken for analysis before irrigation, and test samples were taken on four occasions during and after intervention, from each of 10 patients undergoing transurethral resection of the prostate. Irrigation fluid was also marked with ethanol (1.5% w/v) and the concentration of this agent measured in the blood and expired air of these patients. The absorbed volume was calculated according to the extracellular distribution space of mannitol. RESULTS: Mannitol and sorbitol could be measured in 85% and 73% of the 40 test samples, respectively. The threshold for full sensitivity for breath ethanol concentration to detect absorption was 132 mL. CONCLUSION: This method for detecting serum mannitol and sorbitol represents a valid procedure for confirming and quantifying the absorption of irrigation fluid in the clinic, which agrees closely with the already established ethanol monitoring procedure and which should now be considered as a reference procedure.

Absorption↗
PubMed2002

Relationship between blood pressure and finger photoplethysmographic waveform during oxygen desaturation test: a model fitting approach.

UNLABELLED: A modified 3-element windkessel model was applied to study the relationship between brachial arterial blood pressure and the photoplethysmographic waveform from pulse oximeters. Data were recorded from 12 healthy volunteers who underwent the oxygen desaturation study. During about 30 minutes recording period, the SpO2 value was regulated down till about 70%. After preprocessing, singular value decomposition (SVD) algorithm was then used to get the best fit of the model parameters. RESULT: the fitting error (RMSE) was 1.07 +/- 0.48 mmHg. The time constant of the model shown significant difference between the highest and the lowest saturation group.

Adult↗
PubMed2002

Design and validation of a pulse oximeter calibrator.

The performance of a new calibrator for pulse oximeters is tested with five pulse oximeters from different manufacturers. The calibrator is based on time resolved transmission spectra of human fingers. Finger spectra with different arterial oxygen saturation can be selected to simulate real patients. The results obtained with this calibration device are compared with the results of conventional calibration procedures with volunteers. Beside accuracy tests the suitability for artifact simulation with the new device is discussed. The response of the five tested pulse oximeters is in good agreement with the response of the pulse oximeters connected to real patients. A test procedure for pulse oximeters similar to the conventional desaturation practice is possible; some of the typical artifacts pulse oximetry has to cope with can be simulated easily.

Calibration↗
PubMed2001

Exposure on cell surface and extensive arginine methylation of ewing sarcoma (EWS) protein.

In contrast to the knowledge regarding the function of chimeric Ewing sarcoma (EWS) fusion proteins that arise from chromosomal translocation, the cellular function of the RNA binding EWS protein is poorly characterized. EWS protein had been found mainly in the nucleus. In this report we show that EWS protein is not only found in the nucleus and cytosol but also on cell surfaces. After cell-surface biotinylation, isoelectric focusing of membrane fraction, avidin-agarose extraction of biotinylated proteins, and SDS-polyacrylamide gel electrophoresis, EWS protein was identified by matrix-assisted laser desorption ionization and nanoelectrospray tandem mass spectrometry of in-gel-digested peptides. These analyses revealed that the protein, having repeated RGG motifs, is extensively asymmetrically dimethylated on arginine residues, the sites of which have been mapped by mass spectrometric methods. Out of a total of 30 Arg-Gly sequences, 29 arginines were found to be at least partially methylated. The Arg-Gly-Gly sequence was present in 21 of the 29 methylation sites, and in contrast to other methylated proteins, only 11 (38%) methylated arginine residues were found in the Gly-Arg-Gly sequence. The presence of Gly on the C-terminal side of the arginine residue seems to be a prerequisite for recognition by a protein-arginine N-methyltransferase (PRMT) catalyzing this asymmetric dimethylation reaction. One monomethylarginine and no symmetrically methylated arginine residue was found. The present findings imply that RNA-binding EWS protein shuttles from the nucleus to the cell surface in a methylated form, the role of which is discussed.

Amino Acid Motifs↗
PubMed2001

Emergency medical service transport-induced stress? An experimental approach with healthy volunteers.

This randomized controlled trial was designed to evaluate the effects of simulated emergency medical service (EMS) transport related stress on hemodynamic variables, and catecholamine plasma levels. A total of 32 healthy male volunteers were randomized to being carried by paramedics from a third-floor apartment through a staircase with subsequent high-speed EMS transport with lights and sirens (stress; n = 16); or sitting on a chair for 5 min, and lying on a stretcher for 15 min (control; n = 16). Blood samples and hemodynamic variables were taken in the apartment before transfer, at the ground floor, and at the end of EMS transport in the stress group, and at corresponding time points in the control group. The stress versus control group had both significantly (P < 0.05) higher mean +/- SEM epinephrine (71 +/- 7 versus 37 +/- 3 pg/ml), and norepinephrine (397 +/- 29 versus 299 +/- 28 pg/ml) plasma levels after transport through the staircase. After EMS transport, the stress versus control group had significantly higher epinephrine (48 +/-6 versus 32 +/- 2 pg/ml), but not norepinephrine (214 +/- 20 versus 264 +/- 31 pg/ml) plasma levels. Heart rate increased significantly from 72 +/- 2 to 84 +/- 3 bpm after staircase transport, but not during and after EMS transport. In conclusion, volunteers being carried by paramedics through a staircase had a significant discharge of both epinephrine and norepinephrine resulting in increased heart rate, but only elevated epinephrine plasma levels during EMS transport. Transport through a staircase may reflect more stress than emergency EMS transport.

Adult↗
PubMed2001

Inter-individual differences in cytokine release in patients undergoing cardiac surgery with cardiopulmonary bypass.

Cardiac surgery with cardiopulmonary bypass (CPB) leads to a systemic inflammatory response with secretion of cytokines (e.g. IL-6, TNF-alpha, IL-1 beta and sIL-2R). The objective of the following study was to investigate in vitro and in vivo cytokine responses and white blood cell counts (WBC) of patients with high versus low cytokine secretion after a coronary artery bypass grafting (CABG) procedure. Twenty male patients undergoing elective CABG surgery with CPB under general anaesthesia were enrolled in the study. On the day of surgery (postoperatively), serum levels of TNF-alpha and IL-1 beta were significantly higher in patients of the high IL-6 level group compared to the respective values in the patient group with low IL-6 levels. The inter-individual differences in IL-6 release in patients undergoing CABG surgery with CPB were accompanied by differences in the release of other cytokines, such as TNF-alpha, IL-1 beta and sIL-2R. To understand whether genetic background plays a role in influencing cytokine plasma levels under surgical stress, we examined the distribution of polymorphic elements within the promoter regions of the TNF-alpha and IL-6 genes, and determined their genotype regarding the BAT2 gene and TNF-beta intron polymorphisms. Our preliminary data suggests that regulatory polymorphisms in or near the TNF locus, more precisely the allele set 140/150 of the BAT2 microsatellite marker combined with the G allele at -308 of the TNF-alpha gene, could be one of the genetic constructions providing for a less sensitive response to various stimuli. Our results suggest: (1) close relationships between cytokine release in the postoperative period, and (2) inter-individually varying patterns of cytokine release in patients undergoing CABG surgery with CPB.

Cardiopulmonary Bypass↗
PubMed2000

Empirical calculation of the relative free energies of peptide binding to the molecular chaperone DnaK.

We describe a methodology to calculate the relative free energies of protein-peptide complex formation. The interaction energy was decomposed into nonpolar, electrostatic and entropic contributions. A free energy-surface area relationship served to calculate the nonpolar free energy term. The electrostatic free energy was calculated with the finite difference Poisson-Boltzmann method and the entropic contribution was estimated from the loss in the conformational entropy of the peptide side chains. We applied this methodology to a series of DnaK*peptide complexes. On the basis of the single known crystal structure of the peptide-binding domain of DnaK with a bound heptapeptide, we modeled ten other DnaK*heptapeptide complexes with experimentally measured K(d) values from 0.06 microM to 11 microM, using molecular dynamics to refine the structures of the complexes. Molecular dynamic trajectories, after equilibration, were used for calculating the energies with greater accuracy. The calculated relative binding free energies were compared with the experimentally determined free energies. Linear scaling of the calculated terms was applied to fit them to the experimental values. The calculated binding free energies were between -7.1 kcal/mol and - 9.4 kcal/mol with a correlation coefficient of 0.86. The calculated nonpolar contributions are mainly due to the central hydrophobic binding pocket of DnaK for three amino acid residues. Negative electrostatic fields generated by the protein increase the binding affinity for basic residues flanking the hydrophobic core of the peptide ligand. Analysis of the individual energy contributions indicated that the nonpolar contributions are predominant compared to the other energy terms even for peptides with low affinity and that inclusion of the change in conformational entropy of the peptide side chains does not improve the discriminative power of the calculation. The method seems to be useful for predicting relative binding energies of peptide ligands of DnaK and might be applicable to other protein-peptide systems, particularly if only the structure of one protein-ligand complex is available.

Binding Sites↗
PubMed2000

A prototype device for standardized calibration of pulse oximeters.

OBJECTIVE: To develop and test a method for standardized calibration of pulse oximeters. METHODS: A novel pulse oximeter calibration technique capable of simulating the behavior of real patients is discussed. It is based on an artificial finger with a variable spectral-resolved light attenuator in conjunction with an extensive clinical database of time-resolved optical transmission spectra of patients fingers in the wavelength range 600-1000 nm. The arterial oxygen saturation of the patients at the time of recording was derived by analyzing a corresponding blood sample with a CO-oximeter. These spectra are used to compute the modulation of the light attenuator which is attached to the artificial finger. This calibration method was tested by arbitrarily playing back recorded spectra to pulse oximeters and comparing their display to the value they displayed when the spectra were recorded. RESULTS: We were able to demonstrate that the calibrator could generate physiological signals which are accepted by a pulse oximeter. We also present some experience of playing back recorded patient spectra. The mean difference between the original reading of the pulse oximeters and the display when attached to the calibrator is 1.2 saturation points (displayed oxygen saturation SpO2) with a standard deviation of 1.9 saturation points. CONCLUSIONS: The tests have shown the capabilities of a spectral light modulator for use as a possible calibration standard for pulse oximeters. If some improvements of the current prototype can be achieved we conclude from the experience with the device that this novel concept for the calibration of pulse oximeters is feasible and that it could become an important tool for assessing the performance of pulse oximeters.

Calibration↗
PubMed2000

[In Process Citation]

A main basis of this habilitation thesis is the development of a portable, mains-free measurement device for determining breath ethanol concentrations (BrEC) both during spontaneous breathing and in mechanically ventilated patinets undergoing inhalation anaesthesia, for detecting and quantifying irrigation fluid absorbed during endourological surgical interventions. Here a respired gas has to be measured which compared to other usually measured gases 1) is present in substatially smaller concentrations, 2) is subject to significant influences by temperature and humidity in the expired air, and 3) can only be measured discontinuously in the alveolar air due to technical limitations of the sensor. The basis for investigating accuracy of measurement was not just evaluation of the device using different lung models, but also a comparison with the target parameter "absorbed irrigation fluid" using another further-developed reference procedure, i.e. direct measurement of sorbitol and mannitol concentrations in serum. This has the added advantage that even when ethanol monitoring is not available, another laboratory procedure is indeed available for directly evaluating the absorption of irrigation fluid. In the clinical aspects of this thesis, ethanol monitoring helped show that during transurethral resection of the prostate (TURP) in spontaneously breathing patients undergoing regional anaesthesia, irrigation fluid was intravascularly absorbed not more often, but more rapidly and in larger quantities than it was in mechanically ventilated patients undergoing inhalation anaesthesia. A possible reason for this was the significantly reduced central venous pressure observed in the group of patients undergoing regional anaesthesia. The diagnosis of a delayed extravascular absorption of irrigation fluid during percutaneous nephrolithotripsy (PNL), made with the assistance of the ethanol monitoring, was associated with a significantly prolonged period of hospitalization in the clinic and an increase in opioid requirements. This finding can be explained pathophysiologically by an increased trauma to the kidney with injury to bordering organ structures. As a result of close co-operation with several departments of the Medical University of Lubeck, we now have at our disposal an excellent BrEC-measuring device for detecting and quantifying absorbed irrigation fluid during urosurgical procedures. The results of the clinical studies presented here underscore the value of the newly-developed AlcoMed 3011.

Journal Article↗
PubMed1999

Conversion of aspartate aminotransferase into an L-aspartate beta-decarboxylase by a triple active-site mutation.

The conjoint substitution of three active-site residues in aspartate aminotransferase (AspAT) of Escherichia coli (Y225R/R292K/R386A) increases the ratio of L-aspartate beta-decarboxylase activity to transaminase activity >25 million-fold. This result was achieved by combining an arginine shift mutation (Y225R/R386A) with a conservative substitution of a substrate-binding residue (R292K). In the wild-type enzyme, Arg(386) interacts with the alpha-carboxylate group of the substrate and is one of the four residues that are invariant in all aminotransferases; Tyr(225) is in its vicinity, forming a hydrogen bond with O-3' of the cofactor; and Arg(292) interacts with the distal carboxylate group of the substrate. In the triple-mutant enzyme, k(cat)' for beta-decarboxylation of L-aspartate was 0.08 s(-1), whereas k(cat)' for transamination was decreased to 0.01 s(-1). AspAT was thus converted into an L-aspartate beta-decarboxylase that catalyzes transamination as a side reaction. The major pathway of beta-decarboxylation directly produces L-alanine without intermediary formation of pyruvate. The various single- or double-mutant AspATs corresponding to the triple-mutant enzyme showed, with the exception of AspAT Y225R/R386A, no measurable or only very low beta-decarboxylase activity. The arginine shift mutation Y225R/R386A elicits beta-decarboxylase activity, whereas the R292K substitution suppresses transaminase activity. The reaction specificity of the triple-mutant enzyme is thus achieved in the same way as that of wild-type pyridoxal 5'-phosphate-dependent enzymes in general and possibly of many other enzymes, i.e. by accelerating the specific reaction and suppressing potential side reactions.

Aspartate Aminotransferases↗
PubMed1999

Maturation-induced conformational changes of HIV-1 capsid protein and identification of two high affinity sites for cyclophilins in the C-terminal domain.

Viral incorporation of cyclophilin A (CyPA) during the assembly of human immunodeficiency virus type-1 (HIV-1) is crucial for efficient viral replication. CyPA binds to the previously identified Gly-Pro90 site of the capsid protein p24, but its role remained unclear. Here we report two new interaction sites between cyclophilins and p24. Both are located in the C-terminal domain of p24 around Gly-Pro157 and Gly-Pro224. Peptides corresponding to these regions showed higher affinities (Kd approximately 0.3 microM) for both CyPA and cyclophilin B than the best peptide derived from the Gly-Pro90 site ( approximately 8 microM) and thus revealed new sequence motifs flanking Gly-Pro that are important for tight interaction of peptide ligands with cyclophilins. Between CyPA and an immature (unprocessed) form of p24, a Kd of approximately 8 microM was measured, which corresponded with the Kd of the best of the Gly-Pro90 peptides, indicating an association via this site. Processing of immature p24 by the viral protease, yielding mature p24, elicited a conformational change in its C-terminal domain that was signaled by the covalently attached fluorescence label acrylodan. Consequently, CyPA and cyclophilin B bound with much higher affinities ( approximately 0.6 and 0.25 microM) to the new, i.e. maturation-generated sites. Since this domain is essential for p24 oligomerization and capsid cone formation, CyPA bound to the new sites might impair the regularity of the capsid cone and thus facilitate in vivo core disassembly after host infection.

Amino Acid Sequence↗
PubMed1999

Conversion of tyrosine phenol-lyase to dicarboxylic amino acid beta-lyase, an enzyme not found in nature.

Tyrosine phenol-lyase (TPL), which catalyzes the beta-elimination reaction of L-tyrosine, and aspartate aminotransferase (AspAT), which catalyzes the reversible transfer of an amino group from dicarboxylic amino acids to oxo acids, both belong to the alpha-family of vitamin B6-dependent enzymes. To switch the substrate specificity of TPL from L-tyrosine to dicarboxylic amino acids, two amino acid residues of AspAT, thought to be important for the recognition of dicarboxylic substrates, were grafted into the active site of TPL. Homology modeling and molecular dynamics identified Val-283 in TPL to match Arg-292 in AspAT, which binds the distal carboxylate group of substrates and is conserved among all known AspATs. Arg-100 in TPL was found to correspond to Thr-109 in AspAT, which interacts with the phosphate group of the coenzyme. The double mutation R100T/V283R of TPL increased the beta-elimination activity toward dicarboxylic amino acids at least 10(4)-fold. Dicarboxylic amino acids (L-aspartate, L-glutamate, and L-2-aminoadipate) were degraded to pyruvate, ammonia, and the respective monocarboxylic acids, e.g. formate in the case of L-aspartate. The activity toward L-aspartate (kcat = 0.21 s-1) was two times higher than that toward L-tyrosine. beta-Elimination and transamination as a minor side reaction (kcat = 0.001 s-1) were the only reactions observed. Thus, TPL R100T/V283R accepts dicarboxylic amino acids as substrates without significant change in its reaction specificity. Dicarboxylic amino acid beta-lyase is an enzyme not found in nature.

Amino Acid Sequence↗