Alzheimer s disease,among the most common neurodegenerative disorders,is chara cterized by progressive cognitive impairment.At present,the Alzheimer’s disease main risk remains genetic ris ks,but major environmental ...Alzheimer s disease,among the most common neurodegenerative disorders,is chara cterized by progressive cognitive impairment.At present,the Alzheimer’s disease main risk remains genetic ris ks,but major environmental fa ctors are increasingly shown to impact Alzheimer’s disease development and progression.Microglia,the most important brain immune cells,play a central role in Alzheimer’s disease pathogenesis and are considered environmental and lifestyle"sensors."Factors like environmental pollution and modern lifestyles(e.g.,chronic stress,poor dietary habits,sleep,and circadian rhythm disorde rs)can cause neuroinflammato ry responses that lead to cognitive impairment via microglial functioning and phenotypic regulation.However,the specific mechanisms underlying interactions among these facto rs and microglia in Alzheimer’s disease are unclear.Herein,we:discuss the biological effects of air pollution,chronic stress,gut micro biota,sleep patterns,physical exercise,cigarette smoking,and caffeine consumption on microglia;consider how unhealthy lifestyle factors influence individual susceptibility to Alzheimer’s disease;and present the neuroprotective effects of a healthy lifestyle.Toward intervening and controlling these environmental risk fa ctors at an early Alzheimer’s disease stage,understanding the role of microglia in Alzheimer’s disease development,and to rgeting strategies to to rget microglia,co uld be essential to future Alzheimer’s disease treatments.展开更多
[Objective] This study was conducted to investigate the effect of laundry wastewater on the quality of river water and the dilution purification effect of river water on laundry wastewater. [Method] The effects of lau...[Objective] This study was conducted to investigate the effect of laundry wastewater on the quality of river water and the dilution purification effect of river water on laundry wastewater. [Method] The effects of laundry wastewater on the contents of total nitrogen(TN), total phosphorus(TP), suspended solids(SS), chemical oxygen demand(COD) and linear alkylbenzene sulfonic acid(LAS) were studied in 7 rivers of Shaoxing City. [Result](1) The contents of TN, TP, SS, COD and LAS increased by 92%, 99%, 340%, 351% and 923%, respectively, at the discharging moment of laundry wastewater; and(2) the five pollutional indexes significantly decreased over time, and especially 2 h after the discharge of laundry wastewater, compared with former the discharge of laundry wastewater, the contents of TN, TP, COD and LAS increased by 6%, 11%, 9% and13%, respectively,while the contents of SS still increased by 76%, i.e., SS required a longer time to achieve self-purification. [Conclusion] Laundry wastewater has some influence on thequality of river water, and the self-purification function of river water could effectively remove pollutants.展开更多
Spermidine is a naturally occurring polyamine widely utilized in the prevention and treatment of various diseases.Current spermidine biosynthetic methods have problems such as low efficiency and complex multi-enzyme c...Spermidine is a naturally occurring polyamine widely utilized in the prevention and treatment of various diseases.Current spermidine biosynthetic methods have problems such as low efficiency and complex multi-enzyme catalysis.Based on sequence-structure-function relationships,we engineered the widely studied homospermidine synthase from Blastochloris viridis(BvHSS)and obtained mutants that could catalyze the production of spermidine from 1,3-diaminopropane and putrescine.The specific activities of BvHSS and the mutants D361E and E232D+D361E(E232D-D)were 8.72,46.04 and 48.30 U/mg,respectively.The optimal pH for both mutants was 9.0,and the optimal temperature was 50◦C.Molecular docking and dynamics simulations revealed that mutating aspartic acid at position 361 to glutamic acid narrowed the substrate binding pocket,promoting stable spermidine production.Conversely,mutating glutamic acid at position 232 to aspartic acid enlarged the substrate channel entrance,facilitating substrate entry into the active pocket and enhancing spermidine generation.In whole-cell catalysis lasting 6 h,D361E and E232D-D synthesized 725.3 and 933.5 mg/L of spermidine,respectively.This study offers a practical approach for single-enzyme catalyzed spermidine synthesis and sheds light on the crucial residues influencing homospermidine synthase catalytic activity in spermidine production.展开更多
Lactate dehydrogenase and malate dehydrogenase are the two main alpha-hydroxy acid dehydrogenases in the human body.We investigated the catalytic properties of human lactate dehydrogenase LDHC,LDHL6A and malate dehydr...Lactate dehydrogenase and malate dehydrogenase are the two main alpha-hydroxy acid dehydrogenases in the human body.We investigated the catalytic properties of human lactate dehydrogenase LDHC,LDHL6A and malate dehydrogenase MDH1 on aromatic α-keto acids phenylpyruvic acid,p-hydroxyphenylpyruvic acid and 3,4-dihydroxyphenylpyruvic acid.The optimum temperatures for LDHC,LDHL6A,and MDH1 are 37℃,35℃,and 45℃,respectively;and the optimum pH is 6.5,6.5,and 5.5,respectively.The K_(m)of LDHC for phenylpyruvic acid and 3,4-dihydroxyphenylpyruvic acid were 0.90 mM and 0.92 mM,respectively.LDHL6A has a high affinity for phenylpyruvic acid and 3,4-dihydroxyphenylpyruvic acid with K_(m)of 0.77 mM and 0.80 mM,respectively;MDH1 has an extremely high affinity(K_(m)=0.46 mM)and catalytic efficiency(k_(cat)/K_(m)=23.87 s^(-1)·mM^(-1))for p-hydroxyphenylpyruvic acid.It also has a high affinity for 3,4-dihydroxyphenylpyruvic acid with a K_(m)of 0.90 mM,but with a low affinity for phenylpyruvic acid(K_(m)=3.76 mM).The catalytic properties of human LDHC,LDHL6A,and MDH1 for the abovementioned aromatic α-keto acids may be one of the sources of L-phenyllactic acid,L-p-hydroxyphenyllactic acid,and L-3,4-dihydroxyphenyllactic acid in humans.展开更多
Ethyl(R)-4-chloro-3-hydroxybutyrate((R)-CHBE),as a chiral intermediate,is widely used in the synthesis of various chiral drugs.In this study,we screened two aldo–keto reductases(LP-AKRs)from the probiotic Lactobacill...Ethyl(R)-4-chloro-3-hydroxybutyrate((R)-CHBE),as a chiral intermediate,is widely used in the synthesis of various chiral drugs.In this study,we screened two aldo–keto reductases(LP-AKRs)from the probiotic Lactobacillus plantarum DSM20174,both with a molecular weight of approximately 31 kDa.Both enzymes could reduce 4-chloroacetoacetic acid ethyl ester(COBE)to produce(R)-CHBE with an enantioselectivity value of 99%.When determining the kinetic parameter,the K_(m),K_(cat),and V_(max)of LP-AKR5 and LP-AKR9 were 9.5 mM,7.6 U/mg,3.96 s^(-1)and 8.7 mM,8.59 U/mg,4.47 s^(-1),respectively.Both LP-AKR5 and LP-AKR9 had an optimal reaction pH of 6 and could maintain a high level of stability at pH 6,allowing them to perform well in an acidic environment.LP-AKR5 and LP-AKR9 had optimal reaction temperatures of 30℃and 40℃,respectively.Metal ions had minimal influence on LP-AKR5 and LP-AKR9 enzyme activities.This series of enzymatic properties showed that LP-AKR5 and LP-AKR9 mined from Lactobacillus plantarum DSM20174 could asym-metrically catalyze the synthesis of(R)-CHBE under weakly acidic circumstances,which could maintain product stability and provide a good foundation for industrial production.展开更多
Promoting the sensitivity of mid-infrared(MIR) spectroscopy to the single-photon level is a critical need for investigating photosensitive biological samples and chemical reactions. MIR spectroscopy based on frequency...Promoting the sensitivity of mid-infrared(MIR) spectroscopy to the single-photon level is a critical need for investigating photosensitive biological samples and chemical reactions. MIR spectroscopy based on frequency upconversion is a compelling pioneer allowing high-efficiency MIR spectral measurement with well-developed single-photon detectors, which overcomes the main limitations of high thermal noise of current MIR detectors.However, noise from other nonlinear processes caused by strong pump fields hinders the development of the upconversion-based MIR spectroscopy to reach the single-photon level. Here, a broadband MIR single-photon frequency upconversion spectroscopy is demonstrated based on the temporal-spectral quantum correlation of non-degenerate photon pairs, which is well preserved in the frequency upconversion process and is fully used in extracting the signals from tremendous noise caused by the strong pump. A correlation spectrum broader than660 nm is achieved and applied for the demonstration of sample identification under a low incident photon flux of 0.09 average photons per pulse. The system is featured with non-destructive and robust operation, which makes single-photon-level MIR spectroscopy an appealing option in biochemical applications. ? 2022 Chinese Laser Press.展开更多
In this study,an alkaline protease BaApr1 from the Bacillus altitudinis W3 was chosen to hydrolysis grass carp(Ctenopharyngodon idella)scales.The hydrolysate of alkaline protease BaApr1 exhibited the best antioxidant ...In this study,an alkaline protease BaApr1 from the Bacillus altitudinis W3 was chosen to hydrolysis grass carp(Ctenopharyngodon idella)scales.The hydrolysate of alkaline protease BaApr1 exhibited the best antioxidant activity compared to other protease hydrolysates.The optimal hydrolysis conditions for BaApr1 were an enzyme dosage of 1250 U/g,a hydrolysis time of 7 h,a pH of 9.5 and a temperature of 50℃.Three novel peptides were purified using ultrafiltration,anion exchange chromatography,gel filtration chromatography and ultra-performance liquid chromatography,and their sequences were identified as Tyr-Val-Gln-Ala-Gly-Ala-Ala-Gly-Ala-Ala-Ala-His(SHP2),Val-Lys-Leu-Tyr-Val-Leu-Leu-Val-Pro(SHP4),and Val-Gln-Val-Leu-Ala-Gly-Pro-Val-Val-Lys-Leu-Tyr(SHP5)with molecular weights of 1086.53 Da,1043.69 Da and 1285.79 Da,respectively.Among them,SHP2 exhibited the highest scavenging activity on DPPH;(EC_(50)4.08 mg/mL),ABTS+;(EC_(50)0.23 mg/mL)and HO;(EC_(50)2.78 mg/mL),and the strongest reducing power.Additionally,SHP5 can significantly inhibit lipid peroxidation in the linoleic acid system.In conclusion,three peptides isolated from scales of hydrolysate of grass carp showed great antioxidant activity and might be used as potential food ingredients and pharmaceuticals.展开更多
This study examines the key human resources factors that affect volunteers＇ service performance from the perspectives of volunteers and managers in the Beijing Summer Olympic Games of 2008. Survey data were collected...This study examines the key human resources factors that affect volunteers＇ service performance from the perspectives of volunteers and managers in the Beijing Summer Olympic Games of 2008. Survey data were collected from 1,727 volunteers and 243 managers at the Beijing Olympics test events held at 10 venues between November 2007 and April 2008. Regression analyses and a moderation test were combined to test the hypotheses. A set of high performance work systems （HPWS） for volunteers in the Beijing Summer Olympic Games were developed which include performance management, training, recognition, teamwork and volunteer participation. Volunteer HPWS were positively related to psychological empowerment, which was in turn positively related to service recovery performance. Moreover, transformational leadership moderates the relationship between volunteer HPWS and psychological empowerment in such a way that the relationship is stronger when transformational leadership is at a higher level than when it is at a lower level.Implications and limitations were also discussed.展开更多
L-DOPA is a major drug for the treatment of Parkinson’s disease,and microbial enzymatic synthesis is an essential way for its industrial production.The expression of tyrosine phenol-lyase(TPL)derived from Erwinia her...L-DOPA is a major drug for the treatment of Parkinson’s disease,and microbial enzymatic synthesis is an essential way for its industrial production.The expression of tyrosine phenol-lyase(TPL)derived from Erwinia herbicola under six diferent constitutive promoters in Escherichia coli was studied.The recombinant strain 5 can express TPL well with growth.The optimal medium composition of this strain was as follows:tryptone 18 g/L,yeast extract 28 g/L,glycerol 10 g/L.After the cell culture is completed,the collected cells were used to catalyze the production of L-DOPA,and the concentration can reach 67.9 g/L.展开更多
l-Lactate dehydrogenases can reduce alpha-keto carboxylic acids asymmetrically and generally have a broad substrate spectrum.l-Lactate dehydrogenase gene(LF-l-LDH0845)with reducing activity towards 3,4-dihydroxyphenyl...l-Lactate dehydrogenases can reduce alpha-keto carboxylic acids asymmetrically and generally have a broad substrate spectrum.l-Lactate dehydrogenase gene(LF-l-LDH0845)with reducing activity towards 3,4-dihydroxyphenylpyruvate and phenylpyruvate was obtained from Lactobacillus fermentum JN248.To change the substrate specificity of LDH0845 and improve its catalytic activity towards large substrates,site-directed mutation of Tyr221 was performed by analyzing the amino acids in the active center.Kinetic parameters show that the kcat values of Y221F mutant on 3,4-dihydroxyphenylpyruvate,4-methyl-2-oxopentanoate,and glyoxylate are 1.21 s^(−1),1.35 s^(−1),and 0.72 s^(−1),respectively,which are 420%,150%and 130%of the wild-type LDH0845.This study shows that the mutations of Y221 can significantly change the substrate specificity of LDH0845,making it become a potential tool enzyme for the reduction of alpha-keto carboxylic acids with large functional groups.展开更多
基金supported by the National Natural Science Foundation of China,Nos.82071190 and 82371438(to LC)Innovative Strong School Project of Guangdong Medical University,No.4SG21230G(to LC)Scientific Research Foundation of Guangdong Medical University,No.GDMUM2020017(to CL)。
文摘Alzheimer s disease,among the most common neurodegenerative disorders,is chara cterized by progressive cognitive impairment.At present,the Alzheimer’s disease main risk remains genetic ris ks,but major environmental fa ctors are increasingly shown to impact Alzheimer’s disease development and progression.Microglia,the most important brain immune cells,play a central role in Alzheimer’s disease pathogenesis and are considered environmental and lifestyle"sensors."Factors like environmental pollution and modern lifestyles(e.g.,chronic stress,poor dietary habits,sleep,and circadian rhythm disorde rs)can cause neuroinflammato ry responses that lead to cognitive impairment via microglial functioning and phenotypic regulation.However,the specific mechanisms underlying interactions among these facto rs and microglia in Alzheimer’s disease are unclear.Herein,we:discuss the biological effects of air pollution,chronic stress,gut micro biota,sleep patterns,physical exercise,cigarette smoking,and caffeine consumption on microglia;consider how unhealthy lifestyle factors influence individual susceptibility to Alzheimer’s disease;and present the neuroprotective effects of a healthy lifestyle.Toward intervening and controlling these environmental risk fa ctors at an early Alzheimer’s disease stage,understanding the role of microglia in Alzheimer’s disease development,and to rgeting strategies to to rget microglia,co uld be essential to future Alzheimer’s disease treatments.
基金Supported by Natural Science Foundation of China(31500321)Scientific Research Foundation of Shaoxing University(20145024)
文摘[Objective] This study was conducted to investigate the effect of laundry wastewater on the quality of river water and the dilution purification effect of river water on laundry wastewater. [Method] The effects of laundry wastewater on the contents of total nitrogen(TN), total phosphorus(TP), suspended solids(SS), chemical oxygen demand(COD) and linear alkylbenzene sulfonic acid(LAS) were studied in 7 rivers of Shaoxing City. [Result](1) The contents of TN, TP, SS, COD and LAS increased by 92%, 99%, 340%, 351% and 923%, respectively, at the discharging moment of laundry wastewater; and(2) the five pollutional indexes significantly decreased over time, and especially 2 h after the discharge of laundry wastewater, compared with former the discharge of laundry wastewater, the contents of TN, TP, COD and LAS increased by 6%, 11%, 9% and13%, respectively,while the contents of SS still increased by 76%, i.e., SS required a longer time to achieve self-purification. [Conclusion] Laundry wastewater has some influence on thequality of river water, and the self-purification function of river water could effectively remove pollutants.
文摘Spermidine is a naturally occurring polyamine widely utilized in the prevention and treatment of various diseases.Current spermidine biosynthetic methods have problems such as low efficiency and complex multi-enzyme catalysis.Based on sequence-structure-function relationships,we engineered the widely studied homospermidine synthase from Blastochloris viridis(BvHSS)and obtained mutants that could catalyze the production of spermidine from 1,3-diaminopropane and putrescine.The specific activities of BvHSS and the mutants D361E and E232D+D361E(E232D-D)were 8.72,46.04 and 48.30 U/mg,respectively.The optimal pH for both mutants was 9.0,and the optimal temperature was 50◦C.Molecular docking and dynamics simulations revealed that mutating aspartic acid at position 361 to glutamic acid narrowed the substrate binding pocket,promoting stable spermidine production.Conversely,mutating glutamic acid at position 232 to aspartic acid enlarged the substrate channel entrance,facilitating substrate entry into the active pocket and enhancing spermidine generation.In whole-cell catalysis lasting 6 h,D361E and E232D-D synthesized 725.3 and 933.5 mg/L of spermidine,respectively.This study offers a practical approach for single-enzyme catalyzed spermidine synthesis and sheds light on the crucial residues influencing homospermidine synthase catalytic activity in spermidine production.
文摘Lactate dehydrogenase and malate dehydrogenase are the two main alpha-hydroxy acid dehydrogenases in the human body.We investigated the catalytic properties of human lactate dehydrogenase LDHC,LDHL6A and malate dehydrogenase MDH1 on aromatic α-keto acids phenylpyruvic acid,p-hydroxyphenylpyruvic acid and 3,4-dihydroxyphenylpyruvic acid.The optimum temperatures for LDHC,LDHL6A,and MDH1 are 37℃,35℃,and 45℃,respectively;and the optimum pH is 6.5,6.5,and 5.5,respectively.The K_(m)of LDHC for phenylpyruvic acid and 3,4-dihydroxyphenylpyruvic acid were 0.90 mM and 0.92 mM,respectively.LDHL6A has a high affinity for phenylpyruvic acid and 3,4-dihydroxyphenylpyruvic acid with K_(m)of 0.77 mM and 0.80 mM,respectively;MDH1 has an extremely high affinity(K_(m)=0.46 mM)and catalytic efficiency(k_(cat)/K_(m)=23.87 s^(-1)·mM^(-1))for p-hydroxyphenylpyruvic acid.It also has a high affinity for 3,4-dihydroxyphenylpyruvic acid with a K_(m)of 0.90 mM,but with a low affinity for phenylpyruvic acid(K_(m)=3.76 mM).The catalytic properties of human LDHC,LDHL6A,and MDH1 for the abovementioned aromatic α-keto acids may be one of the sources of L-phenyllactic acid,L-p-hydroxyphenyllactic acid,and L-3,4-dihydroxyphenyllactic acid in humans.
文摘Ethyl(R)-4-chloro-3-hydroxybutyrate((R)-CHBE),as a chiral intermediate,is widely used in the synthesis of various chiral drugs.In this study,we screened two aldo–keto reductases(LP-AKRs)from the probiotic Lactobacillus plantarum DSM20174,both with a molecular weight of approximately 31 kDa.Both enzymes could reduce 4-chloroacetoacetic acid ethyl ester(COBE)to produce(R)-CHBE with an enantioselectivity value of 99%.When determining the kinetic parameter,the K_(m),K_(cat),and V_(max)of LP-AKR5 and LP-AKR9 were 9.5 mM,7.6 U/mg,3.96 s^(-1)and 8.7 mM,8.59 U/mg,4.47 s^(-1),respectively.Both LP-AKR5 and LP-AKR9 had an optimal reaction pH of 6 and could maintain a high level of stability at pH 6,allowing them to perform well in an acidic environment.LP-AKR5 and LP-AKR9 had optimal reaction temperatures of 30℃and 40℃,respectively.Metal ions had minimal influence on LP-AKR5 and LP-AKR9 enzyme activities.This series of enzymatic properties showed that LP-AKR5 and LP-AKR9 mined from Lactobacillus plantarum DSM20174 could asym-metrically catalyze the synthesis of(R)-CHBE under weakly acidic circumstances,which could maintain product stability and provide a good foundation for industrial production.
基金National Key Research and Development Program of China(2021YFA1201503)National Natural Science Foundation of China(11621404,12204174,62175064)+2 种基金Natural Scienceof CQ CSTC2021JCYJ-MAXMX0356Research Funds of Happiness Flower ECNU(2021ST2110)Fundamental Research Funds for the Central Universities。
文摘Promoting the sensitivity of mid-infrared(MIR) spectroscopy to the single-photon level is a critical need for investigating photosensitive biological samples and chemical reactions. MIR spectroscopy based on frequency upconversion is a compelling pioneer allowing high-efficiency MIR spectral measurement with well-developed single-photon detectors, which overcomes the main limitations of high thermal noise of current MIR detectors.However, noise from other nonlinear processes caused by strong pump fields hinders the development of the upconversion-based MIR spectroscopy to reach the single-photon level. Here, a broadband MIR single-photon frequency upconversion spectroscopy is demonstrated based on the temporal-spectral quantum correlation of non-degenerate photon pairs, which is well preserved in the frequency upconversion process and is fully used in extracting the signals from tremendous noise caused by the strong pump. A correlation spectrum broader than660 nm is achieved and applied for the demonstration of sample identification under a low incident photon flux of 0.09 average photons per pulse. The system is featured with non-destructive and robust operation, which makes single-photon-level MIR spectroscopy an appealing option in biochemical applications. ? 2022 Chinese Laser Press.
基金supported by the Collaborative Innovation Involving Production,Teaching&Research Funds of Jiangsu Province(BY2014023-28)。
文摘In this study,an alkaline protease BaApr1 from the Bacillus altitudinis W3 was chosen to hydrolysis grass carp(Ctenopharyngodon idella)scales.The hydrolysate of alkaline protease BaApr1 exhibited the best antioxidant activity compared to other protease hydrolysates.The optimal hydrolysis conditions for BaApr1 were an enzyme dosage of 1250 U/g,a hydrolysis time of 7 h,a pH of 9.5 and a temperature of 50℃.Three novel peptides were purified using ultrafiltration,anion exchange chromatography,gel filtration chromatography and ultra-performance liquid chromatography,and their sequences were identified as Tyr-Val-Gln-Ala-Gly-Ala-Ala-Gly-Ala-Ala-Ala-His(SHP2),Val-Lys-Leu-Tyr-Val-Leu-Leu-Val-Pro(SHP4),and Val-Gln-Val-Leu-Ala-Gly-Pro-Val-Val-Lys-Leu-Tyr(SHP5)with molecular weights of 1086.53 Da,1043.69 Da and 1285.79 Da,respectively.Among them,SHP2 exhibited the highest scavenging activity on DPPH;(EC_(50)4.08 mg/mL),ABTS+;(EC_(50)0.23 mg/mL)and HO;(EC_(50)2.78 mg/mL),and the strongest reducing power.Additionally,SHP5 can significantly inhibit lipid peroxidation in the linoleic acid system.In conclusion,three peptides isolated from scales of hydrolysate of grass carp showed great antioxidant activity and might be used as potential food ingredients and pharmaceuticals.
文摘This study examines the key human resources factors that affect volunteers＇ service performance from the perspectives of volunteers and managers in the Beijing Summer Olympic Games of 2008. Survey data were collected from 1,727 volunteers and 243 managers at the Beijing Olympics test events held at 10 venues between November 2007 and April 2008. Regression analyses and a moderation test were combined to test the hypotheses. A set of high performance work systems （HPWS） for volunteers in the Beijing Summer Olympic Games were developed which include performance management, training, recognition, teamwork and volunteer participation. Volunteer HPWS were positively related to psychological empowerment, which was in turn positively related to service recovery performance. Moreover, transformational leadership moderates the relationship between volunteer HPWS and psychological empowerment in such a way that the relationship is stronger when transformational leadership is at a higher level than when it is at a lower level.Implications and limitations were also discussed.
基金We thank the National Key Scientifc Instrument and Equipment Development Project of China(2013YQ17052504)the Program for Changjiang Scholars and Innovative Research Team in the University of Ministry of Education of China(IRT_15R55)+1 种基金the seventh group of Hundred-Talent Program of Shanxi Province(2015)The Key Project of Research and Development Plan of Shaanxi(2017ZDCXLSF-01-02-01)for fnancial support.
文摘L-DOPA is a major drug for the treatment of Parkinson’s disease,and microbial enzymatic synthesis is an essential way for its industrial production.The expression of tyrosine phenol-lyase(TPL)derived from Erwinia herbicola under six diferent constitutive promoters in Escherichia coli was studied.The recombinant strain 5 can express TPL well with growth.The optimal medium composition of this strain was as follows:tryptone 18 g/L,yeast extract 28 g/L,glycerol 10 g/L.After the cell culture is completed,the collected cells were used to catalyze the production of L-DOPA,and the concentration can reach 67.9 g/L.
基金the National Key Scientific Instrument and Equipment Development Project of China(2013YQ17052504)the Program for Changjiang Scholars and Innovative Research Team in the University of Ministry of Education of China(IRT_15R55)+1 种基金the Natural Science Foundation of Shaanxi province(2019JQ-725)the Postgraduate Research and Practice Innovation Program of Jiangsu Province(KYCX19_1841,KYCX19_1842)for financial support.
文摘l-Lactate dehydrogenases can reduce alpha-keto carboxylic acids asymmetrically and generally have a broad substrate spectrum.l-Lactate dehydrogenase gene(LF-l-LDH0845)with reducing activity towards 3,4-dihydroxyphenylpyruvate and phenylpyruvate was obtained from Lactobacillus fermentum JN248.To change the substrate specificity of LDH0845 and improve its catalytic activity towards large substrates,site-directed mutation of Tyr221 was performed by analyzing the amino acids in the active center.Kinetic parameters show that the kcat values of Y221F mutant on 3,4-dihydroxyphenylpyruvate,4-methyl-2-oxopentanoate,and glyoxylate are 1.21 s^(−1),1.35 s^(−1),and 0.72 s^(−1),respectively,which are 420%,150%and 130%of the wild-type LDH0845.This study shows that the mutations of Y221 can significantly change the substrate specificity of LDH0845,making it become a potential tool enzyme for the reduction of alpha-keto carboxylic acids with large functional groups.
