Találati lista | Tudóstér

001-es BibID:	BIBFORM018946
Első szerző:	Mótyán János András (biokémikus, molekuláris biológus)
Cím:	Transglycosylation by barley alfa-amylase 1 / Mótyán János A., Fazekas Erika, Mori Haruhide, Svensson Birte, Bagossi Péter, Kandra Lili, Gyémánt Gyöngyi
Dátum:	2011
ISSN:	1381-1177
Megjegyzések:	The transglycosylation activity of barley alfa-amylase 1 (AMY1) and active site AMY1 subsite mutant enzymes was investigated. We report here the transferase ability of the V47A, V47F, V47D and S48Y single mutants and V47K/S48G and V47G/S48D double mutant AMY1 enzymes in which the replaced amino acids play important role in substrate binding at subsites at-3 through-5. Although mutation increases the transglycosylation activity of enzymes, in the presence of acceptors the difference between wild type and mutants is not so significant. Oligomer transfer reactions of AMY1 wild type and its mutants were studied using maltoheptaose and maltopentaose donors and different chromophore containing acceptors. The conditions for the chemoenzymatic synthesis of 4-methylumbelliferyl-alfa-d-maltooligosaccharides (MU-alfa-d-MOSs) were optimized using 4-methylumbelliferyl-alfa-d-glucoside as acceptor and maltoheptaose as donor. 4-Methylumbelliferyl-alfa-d-maltoside, -maltotrioside, -maltotetraoside and -maltopentaoside have been synthesized. Products were identified by MALDI-TOF MS. 1H and 13C NMR analyses showed that AMY1 V47F preserved the stereo- and regioselectivity. The produced MU-alfa-d-MOSs of degree of polymerization DP 2, DP 3 and DP 5 were successfully applied to detect activity of Bacillus stearothermophilus maltogenic alfa-amylase, human saliv
Tárgyszavak:	Természettudományok Biológiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban Barley alpha-amylase 1 Transglycosylation Methylumbelliferyl-glycosides Chemoenzymatic synthesis Amylase assay
Megjelenés:	Journal Of Molecular Catalysis B-Enzymatic. - 72 : 3-4 (2011), p. 229-237. -
További szerzők:	Fazekas Erika (1985-) (kémikus) Mori, Haruhide Svensson, Birte Bagossi Péter (1966-2011) (biokémikus, vegyész) Kandra Lili (1943-) (biokémikus) Gyémánt Gyöngyi (1960-) (vegyész)
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
Borító:
Saját polcon:

001-es BibID:	BIBFORM013253
Első szerző:	Mótyán János András (biokémikus, molekuláris biológus)
Cím:	Computer-aided subsite mapping of alpha-amylases / János A. Mótyán, Gyöngyi Gyémánt, János Harangi, Péter Bagossi
Dátum:	2011
Megjegyzések:	Subsite mapping is a crucial procedure in the characterization of alpha-amylases (EC 3.2.1.1), which are extensively used in starch-based industries and in diagnosis of pancreatic and salivary glands disorders. A computer-aided method has been developed for subsite mapping of alpha-amylases, which substitutes the difficult, expensive, and time-consuming experimental determination of action patterns to crystal structures based energy calculations. Interaction energies between enzymes and carbohydrate substrates were calculated after short energy minimization by a molecular mechanics program. A training set of wild type and mutant amylases with known experimental action patterns of 13 enzymes of wide range of origin was used to set up the procedure. Calculations for training set resulted in good correlation in case of subsite binding energies (r2 = 0.827-0.929) and bond cleavage frequencies (r2 = 0.727-0.835). A set of eight novel barley amylase 1 mutants was used to test our model. Subsite binding energies were predicted with r2 = 0.502 correlation coefficient, while bond cleavage frequency prediction resulted in r2 = 0.538. Our computer-aided procedure may supplement the experimental subsite mapping methods to predict and understand characteristic features of alpha-amylases.
Tárgyszavak:	Természettudományok Biológiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban alpha-amylase subsite mapping binding energy bond cleavage frequency molecular modeling
Megjelenés:	Carbohydrate Research. - 346 : 3 (2011), p. 410-415. -
További szerzők:	Gyémánt Gyöngyi (1960-) (vegyész) Harangi János (1950-) (biokémikus, kromatográfus) Bagossi Péter (1966-2011) (biokémikus, vegyész)
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
Borító:
Saját polcon:

001-es BibID:	BIBFORM010529
Első szerző:	Nielsen, Morten M.
Cím:	Two Secondary Carbohydrate Binding Sites on the Surface of Barley alpha-Amylase 1 Have Distinct Functions and Display Synergy in Hydrolysis of Starch Granules / Morten M. Nielsen, Sophie Bozonnet, Eun-Seong Seo, János A. Mótyán, Joakim M. Andersen, Adiphol Dilokpimol, Maher Abou Hachem, Gyöngyi Gyémánt, Henrik Næsted, Lili Kandra, Bent W. Sigurskjold, Birte Svensson
Dátum:	2009
ISSN:	0006-2960
Megjegyzések:	Some polysaccharide processing enzymes possess secondary carbohydrate binding sites situated on the surface far from the active site. In barley alpha-amylase 1 (AMY1), two such sites, SBS1 and SBS2, are found on the catalytic (beta/alpha)8-barrel and the noncatalytic C-terminal domain, respectively. Site-directed mutagenesis of Trp(278) and Trp(279), stacking onto adjacent ligand glucosyl residues at SBS1, and of Tyr(380) and His(395), making numerous ligand contacts at SBS2, suggested that SBS1 and SBS2 act synergistically in degradation of starch granules. While SBS1 makes the major contribution to binding and hydrolysis of starch granules, SBS2 exhibits a higher affinity for the starch mimic beta-cyclodextrin. Compared to that of wild-type AMY1, the K-d of starch granule binding by the SBS1 W278A, W279A, and W278A/W279A mutants thus increased 15-35 times; furthermore, the k(cat)/K-m of W278A/W279A was 2%, whereas both affinity and activity for Y380A at SBS2 were 10% of the wild-type values. Dual site double and triple SBS1/SBS2 substitutions eliminated binding to starch granules, and the k(cat)/K-m of W278A/W279A/Y380A AMY1 was only 0.4% of the wild-type value. Surface plasmon resonance analysis of mutants showed that beta-cyclodextrin binds to SBS2 and SBS1 with K-d,K-1 and K-d,K-2 values of 0.07 and 1.40 mM, respectively. A model that accounts for the observed synergy in starch hydrolysis., where SBS1 and SBS2 bind ordered and free alpha-glucan chains, respectively, thus targeting the enzyme to single alpha-glucan chains accessible for hydrolysis, is proposed. SBS1 and SBS2 also influence the kinetics of hydrolysis for amylose and maltooligosaccharides, the degree of multiple attack on amylose, and subsite binding energies.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Biochemistry. - 48 : 32 (2009), p. 7686-7697. -
További szerzők:	Bozonnet, Sophie Seo, Eun-Seong Mótyán János András (1981-) (biokémikus, molekuláris biológus) Andersen, Joakim M. Dilokpimol, Adiphol Abou Hachem, Maher Gyémánt Gyöngyi (1960-) (vegyész) Naested, Henrik Kandra Lili (1943-) (biokémikus) Sigurskjold, Bent W. Svensson, Birte
Internet cím:	DOI Intézményi repozitóriumban (DEA) tárolt változat Szerző által megadott URL
Borító:
Saját polcon:

001-es BibID:	BIBFORM016486
Első szerző:	Seo, Eun-Seong
Cím:	New Insight into Structure/Function Relationships in Plant alpha-Amylase Family GH13 Members / Eun-Seong Seo, Joakim M. Andersen, Morten M. Nielsen, Malene B. Vester-Christensen, Camilla Christiansen, Johanne M. Jensen, János A. Mótyán, Mikkel A. Glaring, Andreas Blennow, Lili Kandra, Gyöngyi Gyémánt, Štefan Janeček, Richard Haser, Nushin Aghajari, Maher Abou Hachem, Birte Svensson
Dátum:	2010
ISSN:	1344-7882
Megjegyzések:	Two carbohydrate binding surface sites (SBSs) on barley alpha-amylase 1 (AMY1) of glycoside hydrolase family 13 (GH13) displayed synergy in interactions with starch granules, thus being pivotal for hydrolysis of supramolecular substrates. Mutational analysis showed that SBS1 is more critical for the conversion of starch granules, while SBS2 has higher affinity than SBS1 for beta-cyclodextrin (beta-CD). Noticeably, the binding preference of beta-CD to SBS2 differed distinctly from that of maltooligosaccharides to the catalytic nucleophile mutant D180A AMY1. Binding energy maps at subsites -8 through +4 of the active site indicated remarkably elevated affinity due to the Y380A mutation at SBS2. The high-yield AMY2 expression variant A42P, made it possible to show that Tyr378-corresponding to Tyr380 in AMY1-has a role in interactions with starch granules, but not in beta-CD binding. Besides SBSs, dedicated starch binding domains (SBDs) mediate binding to starch granules. SBDs are currently categorised into 9 carbohydrate binding module (CBM) families. A novel CBM20 subfamily encountered in regulatory enzymes possesses characteristically low affinity for beta-CD. Although alpha-amylase is essential for starch mobilisation in germinating barley seeds, efficient degradation requires the concerted action of alpha-amylase, limit dextrinase (LD) and possibly alpha-glucosidase. Limit dextrinase (LD) is encoded by a single gene and represents the sole debranching activity during germination. Recent expression of functional LD in Pichia pastoris makes biochemical and biophysical characterisation of this GH13 enzyme possible. An endogenous limit dextrinase inhibitor was cloned and produced recombinantly and demonstrated to have sub-nanomolar affinity for LD.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban surface binding sites, amylose, starch granules, starch binding domain, limit dextrinase
Megjelenés:	Journal of applied glycoscience. - 57 : 2 (2010), p. 157-162. -
További szerzők:	Andersen, Joakim M. Nielsen, Morten M. Vester-Christensen, Malene B. Christiansen, Camilla Jensen, Johanne M. Mótyán János András (1981-) (biokémikus, molekuláris biológus) Glaring, Mikkel A. Blennow, Andreas Kandra Lili (1943-) (biokémikus) Gyémánt Gyöngyi (1960-) (vegyész) Janeček, Štefan Haser, Richard Aghajari, Nushin Abou Hachem, Maher Svensson, Birte
Internet cím:	elektronikus változat Intézményi repozitóriumban (DEA) tárolt változat
Borító:
Saját polcon: