酶研究进展(英文)最新文献

{"title":"Structural and functional evidence for two separate oligosaccharide binding sites of Pasteurella multocida hyaluronan synthase","authors":"F. Kooy, H. Beeftink, M. Eppink, J. Tramper, G. Eggink, C. Boeriu","doi":"10.4236/AER.2013.14011","DOIUrl":"https://doi.org/10.4236/AER.2013.14011","url":null,"abstract":"Pasteurella multocida hyaluronan synthase (PmHAS) is a bi-functional glycosyltransferase, containing a β1,3-glucuronyltransferase and β1,4-N-acetylglucosaminetransferase domain. PmHAS catalyzes the elongation of hyaluronan (HA) through the sequential addition of single monosaccharides to the non-reducing end of the hyaluronan chain. Research is focused on the relation between the length of the HA oligosaccharide and the single-step elongation kinetics from HA4 up to HA9. It was found that the turnover number kcat increased with length to maximum values of 11 and 14 s-1 for NAc- and UA-transfer, respectively. Interestingly, the specificity constant kcat/KM increased with polymer length from HA5 to HA7 to a value of 44 mM-1s-1, indicating an oligosaccharide binding site with increasing specificity towards a heptasaccharide at the UA domain. The value of kcat/KM remained moderately constant around 8 mM-1s-1 for HA4, HA6, and HA8, indicating a binding site with significantly lower binding specificity at the NAc domain than at the UA domain. These findings are further corroborated by a structural homology model of PmHAS, revealing two distinct sites for binding of oligosaccharides of different sizes, one in each transferase domain. Structural alignment studies between PmHAS and glycosyltransferases of the GT-A fold showed significant similarity in the binding of the UDP-sugars and the orientation of the acceptor substrate. These similarities in substrate orientation in the active site and in essential amino acid residues involved in substrate binding were utilized to localize the two HA oligosaccharide binding sites.","PeriodicalId":65616,"journal":{"name":"酶研究进展(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70484853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Versatility of microbial proteases","authors":"V. Jisha, R. B. Smitha, S. Pradeep, S. Sreedevi, Kizhakkepawothail N. Unni, S. Sajith, P. Priji, M. S. Josh, S. Benjamin","doi":"10.4236/AER.2013.13005","DOIUrl":"https://doi.org/10.4236/AER.2013.13005","url":null,"abstract":"Proteases or peptidases constitute the largest group of enzymes in bio-industry with a long array of uses. They play an invincible role in industrial biotechnology, especially in detergent, food and pharmaceutical arena. This focused review encompasses an overview on alkaline proteases, mainly of microbial sources in a handy module. Following an introduction and general classification with evolutionary insight, major sources of proteases (animal, plant and microbial including fungal, bacterial), their general properties with mechanism of action and molecular masses are discussed. Proteases fromBacillusspp. have been given special attention. In addition to this, an overview on the applications of proteases in detergent, tannery, food, metal recovery and waste treatment industries is also addressed briefly.","PeriodicalId":65616,"journal":{"name":"酶研究进展(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70485123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crystal structure, biochemical and biophysical characterisation of NHR1 domain of E3 Ubiquitin ligase neutralized","authors":"D. Gupta, S. Beaufils, V. Vié, G. Paboeuf, Bill Broadhurst, F. Schweisguth, T. Blundell, V. Bolanos-Garcia","doi":"10.4236/AER.2013.13007","DOIUrl":"https://doi.org/10.4236/AER.2013.13007","url":null,"abstract":"Notch signaling controls diverse developmental decisions of central importance to cell activity. One of the conserved positive regulators of Notch signaling is Neuralized, the E3 Ubiquitin ligase enzyme that regulates signaling activity by endocytosis. Neuralized has two novel repeats, NHR1 and NHR2, with a RING finger motif at the C-terminus. Both endocytosis of the Notch ligand, Delta, and inhibition of Notch signaling by Tom, a bearded family member, require the NHR1 domain. Here we describe the first crystal structure of NHR1 domain from Drosophila melanogaster, solved to 2.1 A resolution by X-ray analysis. Using NMR and other biophysical techniques we define a minimal binding region of Tom, consisting of 12 residues, which interacts with NHR1 and show by interfacial analysis of protein monolayers that NHR1 binds PI4P. Taken together, the studies provide insight into molecular interactions that are important for Notch signaling.","PeriodicalId":65616,"journal":{"name":"酶研究进展(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70484676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetic studies on recombinant stem bromelain","authors":"M. Bala, M. Mel, M. Jami, A. Amid, H. Salleh","doi":"10.4236/AER.2013.13006","DOIUrl":"https://doi.org/10.4236/AER.2013.13006","url":null,"abstract":"Stem bromelain is a plant thiol protease with several industrial and therapeutic applications. This current work presents kinetic studies of recombinant bromelain (recBM) expressed in Escherichia coli BL21-AI on foursynthetic substrates, N-α-carbobenzoxy-L-alanyl-p-nitrophenylester (ZANPE), N-α-carbobenzoxy-L-arginyl-L-ar-ginine-p-nitroanilide (ZAANA), N-α-carbobenzo-xy-L-phenylalanyl-L-valyl-L-arginine-p-nitroanili-de (ZPVANA) and L-pyroglutamyl-L-phenylalanyl-L-leucine-p-nitroanilide (PFLNA). Hydrolytic activities of recBM at various pH and temperature conditions were compared to that of commercial bromelain (cBM). Both enzymes demonstrated high activities at 45o C and pH 5 - 8 for recBM and pH 6 - 8 for cBM. recBM showed marginally lower Kmand slightly higher kcat/Kmfor ZAANA, ZANPE and ZPVANA in comparison to cBM.trans Epoxysuccinyl-L-leucylamido {4- guanidino}butane (E-64) severely affected recBM and cBM hydrolysis of the synthetic substrates by competitive inhibition with Kivalues of 3.6 - 5.1 μM and 5.5 - 6.9 μM for recBM and cBM, respectively. The evaluated properties of recBM including temperature and pH optima, substrate specificity and sensitivity to inhibitors or activators, satisfy the requisites required for food industries.","PeriodicalId":65616,"journal":{"name":"酶研究进展(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70484664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cooperative binding of calcium ions modulates the tertiary structure and catalytic activity of Matrix-Metalloproteinase-9","authors":"Shakila Tobwala, D. Srivastava","doi":"10.4236/AER.2013.12002","DOIUrl":"https://doi.org/10.4236/AER.2013.12002","url":null,"abstract":"To ascertain the molecular basis of Ca2+-mediated activation of matrix metalloproteinase-9 (MMP-9), we determined the accessibility of tryptophan residues to externally added acrylamide as quencher in the absence and presence of the metal ion. The steady-state and time resolved fluorescence data revealed that MMP-9 possesses two classes of tryptophan residues, “exposed” and “buried” which are quenched by the collisional rate constants (kq) of 3.2′ 109M-1.s-1 and 7.5′ 108M-1.s-1, respectively. These values are impaired by approximately two and three-fold, respectively, in the presence of 10 mM Ca2+. The Stern-Volmer constants (Ksv values) predicted from the time resolved fluorescence data (in the absence of Ca2+ ) satisfied the dynamic quenching model of the enzyme’s tryptophan residues. This was not the case in the presence of Ca2+ ; the steady-state acrylamide quenching data could only be explained by a combination of “dynamic” and “static” quenching models. A cumulative account of these data led to the suggestion that the binding of Ca2+ modulated the tertiary structure of the protein by decreasing the dynamic flexibility of the enzyme, which is manifested in further structuring of the enzyme’s active site pocket toward facilitating catalysis. Arguments are presented that the binding of Ca2+ at distal sites “dynamically” communicates with the \u0000active site residues of MMP-9 during catalysis.","PeriodicalId":65616,"journal":{"name":"酶研究进展(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70485054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermostable alkaline protease production from Bacillus pumilus D-6 by using agro-residues as substrates","authors":"B. K. Bajaj, Gaytri Jamwal","doi":"10.4236/AER.2013.12003","DOIUrl":"https://doi.org/10.4236/AER.2013.12003","url":null,"abstract":"Proteases due to their wide range of applications in biotechnological processes have been the  focus of intense research for many decades. However, from industrial application view point most of the available proteases lack desired properties; therefore, search for better and efficient thermostable alkaline proteases are always on. Bacillus pumilus D-6, isolated from dairy plant soil sample, in the current study produced protease which showed activity and stability at high alkaline pH (8 - 12) and high temperatures (70。C- 100。C). Enzyme activity remained unfazed even in presence of inhibitors like Pb2+and Hg2+which are considered universal inhibitors of enzyme activity. Besides, the organism successfully utilized crude agriculture based substrates as carbon and nitrogen source and produced substantial enzyme titre.","PeriodicalId":65616,"journal":{"name":"酶研究进展(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70485107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dexamethasone treatment alters kinetics properties of liver mitochondrial F 0 .F 1 -ATPase and membrane lipid profiles in developing and adult rats","authors":"Jignesh D. Pandya, N. Agarwal, Hiren R Modi, S. Katyare","doi":"10.4236/AER.2013.11001","DOIUrl":"https://doi.org/10.4236/AER.2013.11001","url":null,"abstract":"Dexamethasone—a potent synthetic glucocorticoid—has multiple diagnostic and therapeutic applications in wide range of age groups. However, the side-effects of dexamethasone (Dex) treatment including those on development are becoming increasingly apparent. Since the developmental processes are energy-dependent, we examined the effects of chronic Dex treatment on kinetics properties of liver mitochondrial F0.F1-ATPase and mitochondrial membrane lipid profiles in rats belonging to different developmental age groups (2, 3, 4 and 5 weeks) and in adults (~8 weeks). The animals were treated with a subcutaneous dose of 2 mg of Dex/kg body weight (or saline as vehicle) for three alternative days (at around 7.00 A.M.) prior to the day of sacrifice. Dex treatment resulted in significant reduction in F0.F1-ATPase activity in developmental age groups and in adults as compared to their age-matched vehicle-treated control group. The substrate kinetics analysis of F0.F1-ATPase resolved Km and Vmax values in 3 components in all the control age groups; whereas Dex treatment significantly altered the Km and Vmax values or abolished the entire components in age-specific manner. Dex treatment significantly lowered the energy of activation and altered phase transition temperature (TtoC) in all the developmental age groups and in adults. Dex treatment significantly increased the contents of total phospholipid (TPL), individual phospholipids classes and cholesterol (CHL) in all the developmental age groups whereas opposite pattern was observed in adults. The mitochondrial membrane became more fluidized in the developing age groups (2, 4 and 5 weeks); whereas no change was observed in 3-week and adult groups following Dex treatment. In present study, our data demonstrate comprehensive deleterious effects of chronic Dex treatment on liver mitochondrial membrane structure and F0.F1-ATPase functional properties with respect to energy metabolism. At the same time, our data also warns against excessive repeated use of antenatal DEX in treatments in growing and adult human patients.","PeriodicalId":65616,"journal":{"name":"酶研究进展(英文)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70485014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}