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1.
Creation of thermostable l-tryptophan dehydrogenase by protein engineering and its application for l-tryptophan quantification.
Matsui, D, Asano, Y
Analytical biochemistry. 2019;:57-63
Abstract
l-Tryptophan dehydrogenase is a new NAD+-dependent amino acid dehydrogenase discovered in Nostoc punctiforme. The enzyme is involved in scytonemin biosynthesis and is highly selective toward l-tryptophan. By a growth-dependent molecular evolution technique, a thermostable mutant enzyme was selected successfully. l-Tryptophan concentration in human plasma was successfully determined using the thermostable mutant of l-tryptophan dehydrogenase.
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2.
Metabolic engineering for improving L-tryptophan production in Escherichia coli.
Niu, H, Li, R, Liang, Q, Qi, Q, Li, Q, Gu, P
Journal of industrial microbiology & biotechnology. 2019;(1):55-65
Abstract
L-Tryptophan is an important aromatic amino acid that is used widely in the food, chemical, and pharmaceutical industries. Compared with the traditional synthetic methods, production of L-tryptophan by microbes is environmentally friendly and has low production costs, and feed stocks are renewable. With the development of metabolic engineering, highly efficient production of L-tryptophan in Escherichia coli has been achieved by eliminating negative regulation factors, improving the intracellular level of precursors, engineering of transport systems and overexpression of rate-limiting enzymes. However, challenges remain for L-tryptophan biosynthesis to be cost-competitive. In this review, successful and applicable strategies derived from metabolic engineering for increasing L-tryptophan accumulation in E. coli are summarized. In addition, perspectives for further efficient production of L-tryptophan are discussed.
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3.
Changes in tryptophan and kynurenine pathway metabolites in the blood of children treated with ketogenic diet for refractory epilepsy.
Żarnowska, I, Wróbel-Dudzińska, D, Tulidowicz-Bielak, M, Kocki, T, Mitosek-Szewczyk, K, Gasior, M, Turski, WA
Seizure. 2019;:265-272
Abstract
PURPOSE There is growing evidence to support the role of the kynurenine pathway in the anticonvulsant efficacy of ketogenic diets (KDs) in refractory epilepsy. The aim of the present study was to measure blood levels of tryptophan (TRP) and its kynurenine derivatives and correlate them with seizure reduction after starting the KD in children with refractory epilepsy. METHODS Sixteen children (9 F/7 M; 7.1 ± 5.1 years) with refractory epilepsy were treated with the KDs. Clinical efficacy and metabolic ketosis were monitored throughout the study; blood levels of TRP, kynurenine (KYN), kynurenic acid (KYNA), and 3-OH-kynurenine (3-OH-KYN) were measured at 3, 6, and 12 months on the diet and compared to the pre-KD levels. RESULTS Out of 16 children, 14 attained a ≥50% reduction (responders) in seizure frequency 3 months after starting the KD. In the 14 responders, TRP levels decreased numerically (18-25%) but not significantly (P = 0.077) compared to the pre-KD control values. KYN levels decreased significantly (30-57%; P = 0.001) compared to the pre-KD control levels while KYNA levels significantly increased (38-96%; P < 0.001). KYNA/KYN ratios significantly increased (100-323%; P = 0.003) while 3-OH-KYN levels (P = 0.680) and KYN/TRP ratios (P = 0.385) remained unchanged. Higher concentrations of KYNA and lower concentrations of KYN (P < 0.05) were found in patients who attained a higher reduction in seizure frequencies on the KD. CONCLUSIONS We report a pattern of changes in the blood level of kynurenines in patients with refractory epilepsy who started the KD. The results of this study further support the role of specific kynurenines (e.g. KYNA) in the efficacy of the KD in refractory epilepsy.
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4.
The association of tryptophan and phenylalanine are associated with arsenic-induced skin lesions in a Chinese population chronically exposed to arsenic via drinking water: a case-control study.
Wei, Y, Jia, C, Lan, Y, Hou, X, Zuo, J, Li, J, Wang, T, Mao, G
BMJ open. 2019;(10):e025336
Abstract
OBJECTIVES We investigated the association of specific serum amino acids (AAs) with the odds of arsenic-induced skin lesions (AISL) and their ability to distinguish patients with AISL from people chronically exposed to arsenic. DESIGN Case-control study. SETTING Three arsenic-exposed villages in Wuyuan County, Hetao Plain, Inner Mongolia, China were evaluated. PARTICIPANTS Among the 450 residents aged 18-79 years, who were chronically exposed to arsenic via drinking water, 56 were diagnosed as having AISL (defined as cases). Another 56 participants without AISL, matched by gender and age (±1 year) from the same population, were examined as controls. MAIN OUTCOME MEASURES AND METHODS AA levels were determined by ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry-based metabolomics analysis. Potential confounding variables were identified via a standardised questionnaire and clinical examination. Multivariable conditional logistic regression model and receiver operating characteristic curve analyses were performed to investigate the relationship between specific AAs and AISL. RESULTS Tryptophan and phenylalanine levels were negatively associated with AISL (p<0.05). Compared with that in the first quartile, the adjusted OR of AISL in the second, third and fourth quartiles were decreased by 44%, 88% and 79% for tryptophan and 30%, 80% and 80% for phenylalanine, respectively. The combination of these two higher-level AAs showed the lowest OR for AISL (OR=0.08; 95% CI 0.02 to 0.25; p<0.001). Furthermore, both AAs showed a moderate ability to distinguish patients with AISL from the control, with the area under the curve (AUC; 95% CI) as 0.67 (0.57 to 0.77) for tryptophan and 0.70 (0.60 to 0.80) for phenylalanine (p<0.05). The combined pattern with AUC (95% CI) was 0.72 (0.62 to 0.81), showing a sensitivity of 76.79% and specificity of 58.93% (p<0.001). CONCLUSIONS Specific AAs may be linked to AISL and play important roles in early AISL identification. TRIAL REGISTRATION NUMBER NCT02235948.
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5.
Interaction of carbohydrate-binding modules with poly(ethylene terephthalate).
Weber, J, Petrović, D, Strodel, B, Smits, SHJ, Kolkenbrock, S, Leggewie, C, Jaeger, KE
Applied microbiology and biotechnology. 2019;(12):4801-4812
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Abstract
Poly(ethylene terephthalate) (PET) is one of the most widely applied synthetic polymers, but its hydrophobicity is challenging for many industrial applications. Biotechnological modification of PET surface can be achieved by PET hydrolyzing cutinases. In order to increase the adsorption towards their unnatural substrate, the enzymes are fused to carbohydrate-binding modules (CBMs) leading to enhanced activity. In this study, we identified novel PET binding CBMs and characterized the CBM-PET interplay. We developed a semi-quantitative method to detect CBMs bound to PET films. Screening of eight CBMs from diverse families for PET binding revealed one CBM that possesses a high affinity towards PET. Molecular dynamics (MD) simulations of the CBM-PET interface revealed tryptophan residues forming an aromatic triad on the peptide surface. Their interaction with phenyl rings of PET is stabilized by additional hydrogen bonds formed between amino acids close to the aromatic triad. Furthermore, the ratio of hydrophobic to polar contacts at the interface was identified as an important feature determining the strength of PET binding of CBMs. The interaction of CBM tryptophan residues with PET was confirmed experimentally by tryptophan quenching measurements after addition of PET nanoparticles to CBM. Our findings are useful for engineering PET hydrolyzing enzymes and may also find applications in functionalization of PET.
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The effect of electroconvulsive therapy (ECT) on serum tryptophan metabolites.
Aarsland, TI, Leskauskaite, I, Midttun, Ø, Ulvik, A, Ueland, PM, Oltedal, L, Erchinger, VJ, Oedegaard, KJ, Haavik, J, Kessler, U
Brain stimulation. 2019;(5):1135-1142
Abstract
BACKGROUND Prior studies suggest that activation of the tryptophan catabolism via the kynurenine pathway by proinflammatory cytokines may be involved in the pathophysiology of depression. Electroconvulsive therapy (ECT) is an effective treatment for major depression (MD) with immunomodulation as one of the proposed modes of action. OBJECTIVE The aim of this study was to investigate serum concentrations of tryptophan and kynurenine pathway metabolites in MD patients and healthy controls, and to explore the effect of ECT on components of the kynurenine pathway. METHODS The study included 27 moderately to severely depressed patients referred to ECT. Blood samples were collected prior to treatment and after the completed ECT-series. Baseline samples were also collected from 14 healthy, age- and sex-matched controls. Serum concentrations of tryptophan, kynurenine, 3-hydroxykynurenine (HK), kynurenic acid (KA), xanthurenic acid (XA), anthranilic acid (AA), 3-hydroxyanthranilic acid (HAA), quinolinic acid (QA), picolinic acid (Pic), pyridoxal 5'-phosphat (PLP), riboflavin, neopterin and cotinine were measured. RESULTS Patients with MD had lower levels of neuroprotective kynurenine-pathway metabolites (KA, XA and Pic) and lower metabolite ratios (KA/Kyn and KA/QA) reflecting reduced neuroprotection compared to controls. The concentration of the inflammatory marker neopterin was increased after ECT, along with Pic and the redox active and immunosuppressive metabolite HAA. CONCLUSION In this pilot study, we found increased concentrations of inflammatory marker neopterin and putative neuroprotective kynurenine metabolites HAA and Pic in MD patients after ECT. Further research in larger cohorts is required to conclude whether ECT exerts its therapeutic effects via changes in the kynurenine pathway.
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A solution based on melatonin, tryptophan, and vitamin B6 (Melamil Tripto©) for sedation in newborns during brain MRI.
Picone, S, Ariganello, P, Mondì, V, Di Palma, F, Martini, L, Marziali, S, Fariello, G, Paolillo, P
Italian journal of pediatrics. 2019;(1):122
Abstract
INTRODUCTION Melatonin has been studied and used for several years as a sleep-wake cycle modulator in patients with sleep disorders. Experimental evidence has demonstrated the multiple neuroprotective benefits of this indoleamine secreted by the pineal gland. Melatonin is also used in neurological investigations, for its ability to induce sleep in children. In fact, it favors falling asleep during electroencephalogram, Magnetic Resonance Imaging (MRI), and during brainstem auditory evoked potentials. Previous studies are focused on infants and children. No investigation have been performed in neonates, before or during instrumental assessments. MATERIAL AND METHODS One hundred ten newborns (term and preterm) undergoing brain MRI were enrolled in the study. Thirty minutes before the planned time for the examination, we administered a single dose solution of melatonin- tryptophan-vitamin B6. Twenty minutes after the initial administration of 2 mg, a second dose of 1 mg was administered, if the baby was still awake. If after further 15 min the baby was still not sleeping, an additional dose of 1 mg was administered. RESULTS In 106 patients we obtained adequate sedation without adverse events, allowing us to perform an adequate quality MRI, with a median time of 25 min to reach sleeping. Only in three patients MRI could not be performed. In patients having a large weight, higher doses of melatonin were necessary to reach sleeping. Considering the pro kg dose of melatonin, the average dose that induced sleepiness in neonates was 0,64 ± 0.16 mg/Kg. CONCLUSION A solution based on Melatonin- tryptophan-vitamin B6 can be a helpful sedative to administer to neonates undergoing brain MRI, avoiding the use of anesthetics and achieving adequate assessments.
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How important is tryptophan in human health?
Kałużna-Czaplińska, J, Gątarek, P, Chirumbolo, S, Chartrand, MS, Bjørklund, G
Critical reviews in food science and nutrition. 2019;(1):72-88
Abstract
Tryptophan (Trp) is an amino acid and an essential component of the human diet. It plays a crucial role in many metabolic functions. Clinicians can use Trp levels in the course of diagnosing various metabolic disorders and the symptoms associated with those diseases. Furthermore, supplementation with this amino acid is considered in the treatment of depression and sleep disorders, mainly due to the Trp relationship with the synthesis of serotonin (5-HT) and melatonin. It is also used in helping to resolve cognitive disorders, anxiety, or neurodegenerative diseases. Reduced secretion of serotonin is associated with autism spectrum disorder, obesity, anorexia and bulimia nervosa, and other diseases presenting peripherals symptoms. The literature strongly suggests that Trp has a significant role in the correct functionality of the brain-gut axis and immunology. This information leads to the consideration of Trp as an essential dietary component due to its role in the serotonin pathway. A reduced availability of Trp in diet and nutraceutical supplementation should be considered with greater concern than one might expect. This paper constitutes a review of the more salient aspects gleaned from the current knowledge base about the role of Trp in diseases, associated nutritional disorders, and food science, in general.
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The effects of a sleep/recovery supplement: 'Night Time Recharge' on sleep parameters in young adults.
Simper, T, Gilmartin, M, Allwood, D, Taylor, L, Chappell, A
Nutrition and health. 2019;(4):265-274
Abstract
BACKGROUND Concentrated cherry juice reportedly contains melatonin which, in turn, has been highlighted as an important regulator in initiating sleep. AIM: The present investigation aims to clarify whether Night Time Recharge (NTR), a marketed sleep aid containing cherry extract, improves key sleep parameters in young, active adults with mildly poor sleep. METHODS A double-blind, randomized, placebo-controlled, cross-over study design was employed. Twenty participants (nine female) consumed either NTR or a placebo for seven days. Accelerometers were used to assess sleep quality and physical activity levels. Urinary levels of 6-sulphatoxymelatonin (6-SMT), a marker of melatonin synthesis, was assessed via enzyme-linked immunosorbent assay. RESULTS 6-SMT levels increased following NTR treatment (28.95 ng/ml) compared with placebo (4.0 ng/ml) (p < 0.001). There was also a significant difference (p = 0.047) in dietary tryptophan consumption during the NTR treatment (1236 mg) versus placebo (1149 mg). No trace of melatonin was detected from our analysis of the supplement. NTR had no significant effect on any sleep parameters with the exception of sleep latency (p = 0.001). CONCLUSIONS As chemical analysis of NTR by liquid-chromatography mass-spectrometry identified no detectable melatonin, the tryptophan content of the supplement is a likely reason for improvement in sleep latency. These results are in contrast to previous studies which have found a positive effect on sleep following cherry supplementation. Future work should focus on sleep latency and investigating whether cherry juice is effective in participants with problems in initiating sleep.
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Comparison of the Effect of Tanacethum Parthenium, 5-Hydroxy Tryptophan, and Magnesium (Aurastop) versus Magnesium Alone on Aura Phenomenon and Its Evolution.
Volta, GD, Zavarise, P, Perego, L, Savi, L, Pezzini, A
Pain research & management. 2019;:6320163
Abstract
None of the clinical trials on migraine conducted thus far have focused on the possibility to modulate the phenomenon of aura. Furthermore, whether proper management of aura results in a better control of the headache phase has been poorly investigated. In the setting of a single-center, pilot, clinical trial, we aimed at comparing the effects of Aurastop (a combination of tanacetum parthenium (150 mg extracted at 0.8% = 1.2 mg di of active parthenolide), griffonia simplicifoila (20 mg of 5-hydroxy tryptophan), and magnesium (185 mg of magnesium pidolatum)) with those of magnesium alone (2.25 grams/tablet, corresponding to 184 mg of Mg++) in the treatment of acute attacks of migraine with aura. Between June 2017 and June 2018, 50 consecutive patients (27/23 male/female; mean age, 31 [18-57] years) with at least 3 episodes of aura per year were included (t 0). Participants were instructed to keep track of the following 4 episodes of migraine with aura (t 1) and invited to assume (1) a tablet of Aurastop at the beginning of the following 2 episodes of aura and (2) a magnesium tablet alone at the occurrence of the third and fourth aura attacks. Forty-eight patients (96.0%) had >50% reduction in aura duration when treated with Aurastop vs. 7 patients (14.0%) when treated with magnesium alone (p < 0.001); 48 patients (96.0%) had >50% reduction of aura-related disability when receiving Aurastop vs. 5 patients (10.0%) when treated with magnesium alone (p < 0.001); however, patients receiving Aurastop did not need to take pain killers in 35% of aura attacks vs. 3% when assuming magnesium (p < 0.001). These results support the hypothesis that Aurastop might be effective in interfering with the phenomenon of aura and provide evidence that the clinical benefit attributable to this combination of molecules might be greater than that obtained with single compounds of proven effect on the biology of migraine.