Metabolic engineering combined with site-directed saturated mutations of α-keto acid decarboxylase for efficient production of 6-aminocaproic acid and 1,6-hexamethylenediamine.

6-Aminocaproic acid (6ACA) and 1,6-hexamethylenediamine (HMDA) are key precursors for nylon synthesis, and both are produced using petroleum-based chemical processes. However, the utilization of bio-based raw materials for biological production of monomers is crucial for nylon industry. In this study, we demonstrated that metabolic engineering of Escherichia coli and selected mutations of α-keto acid decarboxylase successfully synthesized 6ACA and HMDA. An artificial iterative cycle from l-lysine to chain-extended α-ketoacids was introduced into Escherichia coli BL21 (DE3). Then, the extended α-ketoacids were decarboxylated and oxidized for 6ACA production. Overexpression of catalase (KatE) combined with the site-directed mutations of α-isopropylmalate synthase (LeuA) contributed synergistic enhancement effect on synthesis of 6ACA, resulting in a 1.3-fold increase in 6ACA titer. Selected mutations in α-keto acid decarboxylase (KivD) improved its specificity and 170.00 ± 5.57 mg/L of 6ACA with a yield of 0.13 mol/mol (6ACA/ l-lysine hydrochloride) was achieved by shake flask cultivation of the engineered strain with the KivD# (F381Y/V461I). Meanwhile, the engineered E. coli could accumulate 84.67 ± 4.04 mg/L of HMDA with a yield of 0.08 mol/mol (HMDA/ l-lysine hydrochloride) by replacing aldehyde dehydrogenase with bi-aminotransferases. This achievement marks a significant advancement in the biological synthesis of 6-carbon compounds, since the biosynthetic pathways of HMDA are rarely identified.

Virtual screening of carboxylic acid reductases for biocatalytic synthesis of 6-aminocaproic acid and 1,6-hexamethylenediamine.

The key precursors for nylon synthesis, that is, 6-aminocaproic acid (6-ACA) and 1,6-hexamethylenediamine (HMD), are produced from petroleum-based feedstocks. A sustainable biocatalytic alternative method from bio-based adipic acid has been demonstrated recently. However, the low efficiency and specificity of carboxylic acid reductases (CARs) used in the process hampers its further application. Herein, we describe a highly accurate protein structure prediction-based virtual screening method for the discovery of new CARs, which relies on near attack conformation frequency and the Rosetta Energy Score. Through virtual screening and functional detection, five new CARs were selected, each with a broad substrate scope and the highest activities toward various di- and ω-aminated carboxylic acids. Compared with the reported CARs, KiCAR was highly specific with regard to adipic acid without detectable activity to 6-ACA, indicating a potential for 6-ACA biosynthesis. In addition, MabCAR3 had a lower Km with regard to 6-ACA than the previously validated CAR MAB4714, resulting in twice conversion in the enzymatic cascade synthesis of HMD. The present work highlights the use of structure-based virtual screening for the rapid discovery of pertinent new biocatalysts.

Benzofurazan -based fluorophore for the spectrofluorimetric determination of 6-Aminocaproic acid: Application to spiked human plasma and urine.

6-Aminocaproic acid is one of the most widely used antihemorrhagic and antifibrinolytic agent, therefore, it is essential to create a novel, sensitive, low cost and straightforward spectrofluorimetric method for its determination. The nucleophilic substitution interaction between the primary amine of 6-aminocaproic acid with 4-chloro-7-nitro benzofurazan (NBD-Cl) generated a yellow product. The reaction proceeded in borate buffer (pH 9) and its fluorescence has been measured at 525 nm after excitation at 472 nm. All of the parameters that have impact on the performance of the developed method were investigated and optimized. The range of linearity was 0.1-0.7 µg/mL while, the quantitation limit was down to 0.101 µg/mL and limit of detection was 0.033 µg/mL. This approach was effectively employed to evaluate the content of 6-aminocaproic acid in laboratory prepared dosage form with average percentage recovery of 100.19 ± 0.72% without any interference from basic excipients. Moreover, the proposed method was extended to determine 6-aminocaproic acid in spiked human plasma and urine.

Thermostable D-amino acid decarboxylases derived from Thermotoga maritima diaminopimelate decarboxylase.

Diaminopimelate decarboxylases (DAPDCs) are highly selective enzymes that catalyze the common final step in different lysine biosynthetic pathways, i.e. the conversion of meso-diaminopimelate (DAP) to L-lysine. We examined the modification of the substrate specificity of the thermostable decarboxylase from Thermotoga maritima with the aim to introduce activity with 2-aminopimelic acid (2-APA) since its decarboxylation leads to 6-aminocaproic acid (6-ACA), a building block for the synthesis of nylon-6. Structure-based mutagenesis of the distal carboxylate binding site resulted in a set of enzyme variants with new activities toward different D-amino acids. One of the mutants (E315T) had lost most of its activity toward DAP and primarily acted as a 2-APA decarboxylase. We next used computational modeling to explain the observed shift in catalytic activities of the mutants. The results suggest that predictive computational protocols can support the redesign of the catalytic properties of this class of decarboxylating PLP-dependent enzymes.

An innovational validated spectrofluorimetric technique for determination of 6-Aminocaproic acid in pure form and its tablet: Application to spiked human plasma and urine.

An innovative and sensitive spectrofluorimetric method has been developed for determination of 6-aminocaproic acid (ACA) in its pure form and its laboratory prepared tablets. The aim of this method is the reaction of ethyl acetoacetate and formaldehyde with the primary amino group presented in ACA as aimed in the Hantzsch reaction, this reaction resulted in formation of a yellow fluorescent dihydropyridine derivative that can be easily detected spectrofluorimetrically at 438 nm (excitation at 358 nm). At the optimum conditions of the reaction, the linear range was found to be (0.7-3.5 µg\mL) with limit of detection is 0.231 µg\mL and limit of quantitation is 0.700 µg\mL. The proposed method used for detection of ACA laboratory prepared tablets with average percentage 100.721 ±â€¯0.701% without any interference from any excipients. This method used for in vitro determination of ACA in spiked human plasma with a percent mean recovery 99.874 ±â€¯1.416%. In addition, the developed method used for determination of ACA in spiked human urine with percent mean recovery 100.314 ±â€¯1.793%.

Catalytic and structural properties of ATP-dependent caprolactamase from Pseudomonas jessenii.

Caprolactamase is the first enzyme in the caprolactam degradation pathway of Pseudomonas jessenii. It is composed of two subunits (CapA and CapB) and sequence-related to other ATP-dependent enzymes involved in lactam hydrolysis, like 5-oxoprolinases and hydantoinases. Low sequence similarity also exists with ATP-dependent acetone- and acetophenone carboxylases. The caprolactamase was produced in Escherichia coli, isolated by His-tag affinity chromatography, and subjected to functional and structural studies. Activity toward caprolactam required ATP and was dependent on the presence of bicarbonate in the assay buffer. The hydrolysis product was identified as 6-aminocaproic acid. Quantum mechanical modeling indicated that the hydrolysis of caprolactam was highly disfavored (ΔG0 '= 23 kJ/mol), which explained the ATP dependence. A crystal structure showed that the enzyme exists as an (αß)2 tetramer and revealed an ATP-binding site in CapA and a Zn-coordinating site in CapB. Mutations in the ATP-binding site of CapA (D11A and D295A) significantly reduced product formation. Mutants with substitutions in the metal binding site of CapB (D41A, H99A, D101A, and H124A) were inactive and less thermostable than the wild-type enzyme. These residues proved to be essential for activity and on basis of the experimental findings we propose possible mechanisms for ATP-dependent lactam hydrolysis.

Progress in the metabolic engineering of bio-based lactams and their ω-amino acids precursors.

Lactams, cyclic carboxamide acids, are important building blocks as monomers for the manufacture of polyamides (nylons), with a market of millions of tons per year. Likewise, their non-natural building blocks, straight chain ω-amino acids, also have a wide range of applications as pharmaceuticals, therapeutic agents, and precursors to other platform chemicals. Current industrial lactam production requires petrochemically-derived routes that involve the use of harsh chemicals and reaction conditions. Microbial production provides a more sustainable method for production, from cost effective renewable resources. This review provides an extensive overview of progress toward the microbial production of lactams, particularly 4C butyrolactam, 5C valerolactam and 6C caprolactam, and their ω-amino acid precursors. Additionally, recent advances in the field as well as proposed microbial production pathways will be discussed, as well as future perspectives for the production of these important bulk chemicals.

An Arthrobacter citreus strain suitable for degrading ε-caprolactam in polyamide waste and accumulation of glutamic acid.

ε-Caprolactam-a toxic xenobiotic compound present in industrial polyamide waste was found to be degraded by caprolactam-degrading bacteria. Arthrobacter citreus was able to utilize up to 20 g ε-caprolactam/l as the sole source of carbon more efficiently as compared to the other Gram positive caprolactam-degrading bacteria Rhodococcus rhodochrous and Bacillus sphaericus. The cells of A. citreus remained viable in medium up to 40 g caprolactam/l. The degradation of 10 g caprolactam/l by A. citreus, when supplied as the sole source of carbon and nitrogen lead to the formation of 6-aminocaproic acid which was detected in broth and there was also an increase in the ammonium content. One of the other metabolites found to consistently accumulate in extracellular medium during the utilization of caprolactam by A. citreus was glutamic acid, though not reported in case of other caprolactam-degrading bacteria. A. citreus could metabolise caprolactam to form non toxic products such as 6-aminocaproic acid and glutamic acid which are amino acids of physiological and commercial importance. In the presence of 6-aminocaproic acid, the rate of caprolactam utilization by A. citreus was decreased but not inhibited and the viable count of cells was found to increase using both the substrates simultaneously. A. citreus was also suitable for degradation of caprolactam in presence of low phosphate as prevalent in soil, and in sterile soil without the supplementation of any other carbon or nitrogen, as well as in native non sterile soil where other microorganisms are present.

The ethanol extract of Zizyphus jujuba var. spinosa seeds ameliorates the memory deficits in Alzheimer's disease model mice.

ETHNOPHARMACOLOGICAL RELEVANCE: The seeds of Zizyphus jujuba var. spinosa (Bunge) Hu ex H.F. Chow (Rhamnaceae) have long been treated as hypnotic agent for sleep disturbances in traditional Chinese and Korean medicine and many previous studies have focused on its effect in central nervous system. AIMS OF STUDY: The present study aimed to provide evidence showing that the ethanol extract of Zizyphus jujuba var. spinosa seeds (EEZS), which may regulate plasmin activity, has the potential to serve as a therapeutic agent for AD. MATERIALS AND METHODS: Synaptic function was determined by measuring long-term potentiation (LTP) in Shaffer-collateral pathway of the hippocampus. Protein levels of plasmin or plasminogen were examined using western blotting. Plasmin activity was measured using ELISA. Cognitive functions were measured using passive avoidance and object recognition tests in the 5XFAD mice. RESULTS: Our in vitro analysis revealed that EEZS-treated hippocampal slices from 5XFAD mice, a mouse model of AD, showed significantly higher long-term potentiation levels than did vehicle-treated hippocampal slices from 5XFAD mice (P < 0.05). Additionally, EEZS significantly elevated the plasmin level and activity in the hippocampal slices from 5XFAD mice (P < 0.05). Co-treating the slices with EEZS and 6-aminocaproic acid, a plasmin inhibitor, blocked the ameliorating effects of EEZS on the synaptic deficits that were present in 5XFAD mice. Compatible with the in vitro study, the results of our in vivo investigation showed that administering EEZS orally to 5XFAD mice ameliorated their memory impairments. Orally administered EEZS also elevated the plasmin level and activity in the hippocampus of 5XFAD mice. CONCLUSIONS: Collectively, our findings suggest that EEZS alleviates the AD-like symptoms in 5XFAD mice by regulating of plasmin activity and EEZS may be a suitable treatment for AD.

Synthesis and Evaluation of Biotinylated Small Molecular Drugs with Long Chain / 中国药学杂志

OBJECTIVE: To set up an easy and effective method for biotinylation of small molecule drugs with long chain. METHODS: Biotinylated 6-aminocaproic acid was synthesized as intermediate by one step method, doxorubicin(DOX) with auto-fluorescence was used as the first drug, and by DCC and DMAP catalysis, biotinylated DOX was synthesized. Using the double fluorescence system of DOX, the binding ability of biotinylated DOX to avidin and its biological activity were determined. When verified to be reasonable and effective, the method was applied to catalyze biotinylated paclitexal (PTX) which didn′t have auto-fluorescence itself, and the physical and chemical characteristics, and biological activities as well as the visualization were tested. RESULTS: The binding rate of synthesized DOX to avidin was 93.7%; the cells inhibition rate and localization were the same as DOX; the purity of biotinylated PTX was 84.42%, and the structure shown by NMR was correct; the cell inhibition rate was the same as PTX; the combination of PTX with microtubules was observed by visual modification. CONCLUSION: The method supplies a temperate way for biotinylation, and can be used for the synthesis and visualization of small molecules as probes and research of drug mechanism.

Surface modification of polyisobutylene via grafting amino acid-based poly (acryloyl-6-aminocaproic acid) as multifunctional material.

Amino acid-based P(acryloyl-6-aminocaproic acid) (PAACA) brushes were fabricated on polyisobutylene (PIB) surface combined with plasma pre-treatment and UV-induced grafting polymerization to construct an antifouling and functional material. The hydrophilicity and hemocompatibility of PIB were largely improved by surface modification of AACA, which were confirmed by water contact angle and platelet adhesion, respectively. PAACA brushes were precisely located onto the surface of PIB to create a patterned PIB-g-PAACA structure, and then the carboxyl groups on PAACA was activated to immobilize functional protein-Concanavalin A (Con A). The obtained Con A-coupled microdomains could further capture erythrocytes. This method developed a platform on commercial PIB surface via amino acid-based polymer brushes which had a promising application in drug delivery and disease diagnosis.

Metabolic Engineering toward Sustainable Production of Nylon-6.

Nylon-6 is a bulk polymer used for many applications. It consists of the non-natural building block 6-aminocaproic acid, the linear form of caprolactam. Via a retro-synthetic approach, two synthetic pathways were identified for the fermentative production of 6-aminocaproic acid. Both pathways require yet unreported novel biocatalytic steps. We demonstrated proof of these bioconversions by in vitro enzyme assays with a set of selected candidate proteins expressed in Escherichia coli. One of the biosynthetic pathways starts with 2-oxoglutarate and contains bioconversions of the ketoacid elongation pathway known from methanogenic archaea. This pathway was selected for implementation in E. coli and yielded 6-aminocaproic acid at levels up to 160 mg/L in lab-scale batch fermentations. The total amount of 6-aminocaproic acid and related intermediates generated by this pathway exceeded 2 g/L in lab-scale fed-batch fermentations, indicating its potential for further optimization toward large-scale sustainable production of nylon-6.

Comparison between the clot-protecting activity of a mutant plasminogen activator inhibitor-1 with a very long half-life and 6-aminocaproic acid.

Plasminogen activator inhibitor (PAI)-1 is a serpin glycoprotein that can stabilize blood clots by inhibiting fibrinolysis. However, wild-type PAI-1 has the disadvantage of a short half-life of ∼2 h. A very long half-life (VLHL) PAI-1 mutant was developed previously with an active-form half-life of >700 h, making it a possible candidate for use in hemorrhagic therapy. Current treatments for mitigating hemorrhage, other than inducers of blood clotting, are limited to lysine analog antifibrinolytics, including 6-aminocaproic acid and tranexamic acid. VLHL PAI-1 has been previously demonstrated to limit bleeding; however, the efficacy of this protein compared with lysine analog antifibrinolytics has not been investigated. The aim of the current study was to compare the clot stabilizing properties of the novel antifibrinolytic VLHL PAI-1 with those of 6-aminocaproic acid in reference plasma. Using thromboelastographic analysis, VLHL PAI-1 exhibited an IC50 (half maximal inhibitory concentration) of 8.8×10-8 mol/l, while 6-aminocaproic acid showed an IC50 of 1.6×10-4 mol/l. However, at doses of >9.0×10-7 mol/l, VLHL PAI-1 exhibited a delay in the onset of clot formation, which may be attributed to thrombin inhibition by excess PAI-1. The inhibition of tissue plasminogen activator by VLHL PAI-1 demonstrated improved efficacy over 6-aminocaproic acid in mitigating hemorrhage. In addition, patients with a PAI-1 deficiency, which causes blood clots to lyse rapidly resulting in profuse bleeding, may benefit from the application of VLHL PAI-1 as an antihemorrhagic therapy.

A new pyruvate oxidase biosensor based on 3-mercaptopropionic acid/6-aminocaproic acid modified gold electrode.

In the biosensor construction, 3-mercaptopropionic acid (3-MPA) and 6-aminocaproic acid (6-ACA) were used for forming self-assembled monolayer (SAM) on a gold disc electrode and pyruvate oxidase was immobilized on the modified electrode surface by using glutaraldehyde. Biosensor response is linearly related to pyruvate concentration at 2.5-50 µM, detection limit is 1.87 µM and response time of the biosensor is 6 s for differential pulse voltammograms. From the repeatability studies (n = 6) for 30.0 µM pyruvate revealed that the average value ([Formula: see text]), standard deviation (S.D) and coefficient of variation (CV %) were calculated to be 31.02 µM, ± 0.1914 µM and 0.62%, respectively.

Implantação de protocolo institucional para o uso racional de hemoderivados e seu impacto no pós-operatório de cirurgias de revascularização miocárdica / Implementation of an institutional protocol for rational use of blood products and its impact on postoperative of coronary artery bypass graft surgery

OBJETIVO: Cirurgias cardíacas são, por vezes, acompanhadas de perdas sanguíneas significativas, e transfusões de sangue podem ser necessárias. No entanto, o uso indiscriminado de hemoderivados pode resultar em efeitos danosos para o paciente. Neste estudo, avaliamos os efeitos imediatos da implantação de um protocolo para o uso racional de hemoderivados no perioperatório de cirurgias de revascularização miocárdica. MÉTODOS: Entre os meses de abril e junho de 2011, foi implementado um protocolo institucional em um hospital privado especializado em cardiologia com a anuência e a colaboração de sete equipes de cirurgia cardíaca, visando ao uso racional de hemoderivados. Foram verificados dados clínicos e demográficos dos pacientes, e avaliados o uso de hemoderivados e os desfechos clínicos no período intra-hospitalar, antes e após a implantação do protocolo. O protocolo consistiu em uma campanha institucional junto às equipes cirúrgicas, de anestesiologia e intensivistas, para difundir a prática do uso de hemoderivados com base em critérios clínicos objetivos (anemia com repercussões hemodinâmicas e disfunção ventricular significativa), bem como tornar rotineira a prescrição de ácido epsilon-aminocaproico no intraoperatório, que é prática recomendada por diretrizes internacionais baseadas em evidência científica. RESULTADOS: Após os 3 meses de implantação do protocolo, houve aumento do uso de ácido epsilon-aminocaproico de 31% para 100%. Antes da implantação do protocolo, 67% das cirurgias utilizaram alguma transfusão sanguínea; após a implantação, 40% das cirurgias necessitaram de alguma transfusão sanguínea nos meses subsequentes do mesmo ano (p<0,001). Não houve diferença significativa nos desfechos clínicos avaliados antes e após implantação do protocolo. CONCLUSÃO: O uso racional de hemoderivados, associado à infusão do ácido epsilon-aminocaproico, tem o potencial de reduzir o número de hemotransfusões no perioperatório de cirurgias cardíacas...

OBJECTIVE: Cardiac surgeries are sometimes followed by significant blood loss, and blood transfusions may be necessary. However, indiscriminant use of blood components can result in detrimental effects for the patient. We evaluated the short-term effects of implementation of a protocol for the rational use of blood products in the perioperative period of cardiac surgery. METHODS: Between April and June 2011, an institutional protocol was implemented in a private hospital specializing in cardiology to encourage rational use of blood products, with the consent and collaboration of seven cardiac surgery teams. We collected clinical and demographic data on the patients. The use of blood products and clinical outcomes were analyzed during hospital stay before and after protocol implementation. The protocol consisted of an institutional campaign with an educational intervention to surgical and anesthesiology teams; the goal was to tailor blood transfusion practice according to clinical goals (anemia with hemodynamic changes and significant ventricular dysfunction) and to make routine the prescription of å-aminocaproic acid intraoperatively, which is recommended by international guidelines based on scientific evidence. RESULTS: After three months of protocol implementation, the use of å-aminocaproic acid increased from 31% to 100%. A total of 67% of surgeries before protocol implementation required any blood transfusion, compared with 40% that required any blood transfusion after protocol implementation in subsequent months of the same year (p<0.001). There was no significant difference in clinical outcomes assessed before and after implementation of the protocol. CONCLUSION: The rational use of blood products associated with infusion of å-aminocaproic acid has the potential to reduce the number of blood transfusions in perioperative of cardiac surgeries, but it can affect the risk of complications.

Antifibrinolítico em cirurgia cardíaca: como e quando usar? / Anfibrinolytic in cardiac surgery: how and when to use?

O sangramento pós-operatório continua sendo uma das principais complicações em cirurgia cardíaca. A etiologia desse sangramento é multifatorial, com hiperfibrinólise e disfunção plaquetária desempenhando papel fundamental Tendo em vista essas causas, as drogas antifibrinolíticas têm sido preconizadas. Desde a retirada da aprotinina do mercado, o ácido epsilon-aminocaproico e o ácido tranexâmico passaram a ser os únicos representantes disponíveis dessa classe de drogas. Essas medicações diminuem a perda de sangue e agem na resposta inflamatória associada ao procedimento cirúrgico. A eficácia variável dessas drogas ocorre devido aos vários esquemas terapêuticos e níveis séricos existentes. Recentemente têm surgido alguns questionamentos na literatura a respeito das complicações, doses, vias de administração e melhor momento para administração desses agentes...

The postoperative bleeding remains a major complication in cardiac surgery. The etiology of this bleeding is multifactorial, with hyperfibrinolysis and platelet dysfunction playing a key role. Given these causes antifibrinolytic drugs have been recommended Since the with drawal of aprotinin in the market, epsilon-aminocaproic acid and tranexamic acid became the sole representatives of this class of drugs available. These medications reduce blood loss and act on the inflammatory response associated with surgery. The variable efficacy of these drugs is due to multiple drug regimens and serum available. Recently some questions have arisen in the literature regarding the comptications, doses, routes of administration and timing for administration of these agents...

Uso del ácido épsilon aminocaproico en cirugía torácica electiva / I use of the sour épsilon aminocaproico in elective thoracic surgery

Se realizó un estudio no observacional, de tipo ensayo clínico terapéutico, comparativo, prospectivo y aleatorizado a 60 pacientes a quienes se les realizó cirugía torácica electiva, con el objetivo de evaluar la eficacia del ácido épsilon aminocaproico (AEAC) en cuanto a la disminución del sangramiento posoperatorio y las transfusiones homólogas en este período, así como describir sus posibles reacciones indeseables. Se encontró que la cantidad de sangre colectada en el posoperatorio fue significativamente menor en el grupo tratado con AEAC que en el control tanto a las 6 como a las 24 horas de finalizada la intervención. Las unidades de glóbulos transfundidas en el transoperatorio fueron semejantes en los 2 grupos, pero la cantidad de glóbulos administrados en el posoperatorio resultó significativamente menor en el grupo estudio, al igual que la proporción de pacientes que necesitó transfusión homóloga en este grupo. No se hallaron diferencias entre ambos grupos en cuanto a las reacciones indeseables(AU)

A randomized, prospective and comparative clinicotherapeutic trial was conducted as part of a non-observational study that included 60 patients who underwent elective thoracic surgery in order to evaluate the effectiveness of epsilon aminocaproic acid (EACA) in connection with the decrease of postoperative bleeding and homologous transfusions in this period, as well as to describe its potential undesirable reactions. It was found that the quantity of blood collected in the postoperaive period was much lower in the group treated with EACA than in the control group, both at 6.00 and at 24.00 hrs postintervention. The units of red blood cells transfunded in the transoperative period were similar in both groups, but the quantity of red blood cells administered in the postoperative was significantly lower in the study group, as well as the proportion of patients requiring homologous transfusions in this group. There were no differences between both groups as for undesirable reactions(AU)