scholarly journals Dual Substrate Specificity of the Rutinosidase from Aspergillus niger and the Role of Its Substrate Tunnel

2020 ◽  
Vol 21 (16) ◽  
pp. 5671
Author(s):  
Katerina Brodsky ◽  
Michal Kutý ◽  
Helena Pelantová ◽  
Josef Cvačka ◽  
Martin Rebroš ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Molecular Modeling ◽  
Aspergillus Niger ◽  
Pichia Pastoris ◽  
Substrate Specificity ◽  
Catalytic Properties ◽  
Dual Substrate Specificity ◽  
New Compounds ◽  
Dual Substrate

Rutinosidases (α-l-rhamnopyranosyl-(1-6)-β-d-glucopyranosidases, EC 3.2.1.168, CAZy GH5) are diglycosidases that cleave the glycosidic bond between the disaccharide rutinose and the respective aglycone. Similar to many retaining glycosidases, rutinosidases can also transfer the rutinosyl moiety onto acceptors with a free –OH group (so-called transglycosylation). The recombinant rutinosidase from Aspergillus niger (AnRut) is selectively produced in Pichia pastoris. It can catalyze transglycosylation reactions as an unpurified preparation directly from cultivation. This enzyme exhibits catalytic activity towards two substrates; in addition to rutinosidase activity, it also exhibits β-d-glucopyranosidase activity. As a result, new compounds are formed by β-glucosylation or rutinosylation of acceptors such as alcohols or strong inorganic nucleophiles (NaN3). Transglycosylation products with aliphatic aglycones are resistant towards cleavage by rutinosidase, therefore, their side hydrolysis does not occur, allowing higher transglycosylation yields. Fourteen compounds were synthesized by glucosylation or rutinosylation of selected acceptors. The products were isolated and structurally characterized. Interactions between the transglycosylation products and the recombinant AnRut were analyzed by molecular modeling. We revealed the role of a substrate tunnel in the structure of AnRut, which explained the unusual catalytic properties of this glycosidase and its specific transglycosylation potential. AnRut is attractive for biosynthetic applications, especially for the use of inexpensive substrates (rutin and isoquercitrin).

scholarly journals Dual-substrate Specificity Short Chain Retinol Dehydrogenases from the Vertebrate Retina

2002 ◽  
Vol 277 (47) ◽  
pp. 45537-45546 ◽  
Author(s):  
Françoise Haeseleer ◽  
Geeng-Fu Jang ◽  
Yoshikazu Imanishi ◽  
Carola A. G. G. Driessen ◽  
Masazumi Matsumura ◽  
...  
Keyword(s):  
Substrate Specificity ◽  
Short Chain ◽  
Vertebrate Retina ◽  
Dual Substrate Specificity ◽  
Dual Substrate

Rhenium and manganese modified activated carbon as catalyst for methanol decomposition

2007 ◽  
Vol 85 (2) ◽  
pp. 118-123 ◽  
Author(s):  
T Tsoncheva ◽  
S Vankova ◽  
O Bozhkov ◽  
D Mehandjiev
Keyword(s):  
Catalytic Activity ◽  
Activated Carbon ◽  
Carbon Materials ◽  
Catalytic Properties ◽  
Methanol Decomposition ◽  
Complex Character ◽  
Active Centre ◽  
Modified Activated Carbon

Bicomponent manganese and rhenium modified activated carbon materials, prepared by different methods, are studied and compared with the corresponding monocomponent materials as catalysts in methanol decomposition to CO and hydrogen. The best catalytic activity and stability is observed for the sample obtained by simultaneous deposition of Mn and Re precursors. The complex character of the catalytic active centre, including manganese and rhenium irons in various oxidative states, is discussed. The determining role of the Mn(II) ions in the improvement of the catalytic properties is assumed.Key words: rhenium, manganese, activated carbon, methanol decomposition.

scholarly journals Synthesis of Novel Heteroleptic Oxothiolate Ni(II) Complexes and Evaluation of Their Catalytic Activity for Hydrogen Evolution

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 401
Author(s):  
Fotios Kamatsos ◽  
Kostas Bethanis ◽  
Christiana A. Mitsopoulou
Keyword(s):  
Catalytic Activity ◽  
Catalytic Properties ◽  
Spectroscopic Methods ◽  
Electrochemical Studies ◽  
X Ray Diffraction ◽  
Neutral Form ◽  
Proton Reduction ◽  
X Ray ◽  
Better Than

Two heteroleptic nickel oxothiolate complexes, namely [Ni(bpy)(mp)] (1) and [Ni(dmbpy)(mp)] (2), where mp = 2-hydroxythiophenol, bpy = 2,2′-bipyridine and dmbpy = 4,4′-dimethyl-2,2′-bipyridine were synthesized and characterized with various physical and spectroscopic methods. Complex 2 was further characterized by single crystal X-ray diffraction data. The complex crystallizes in the monoclinic P 21/c system and in its neutral form. The catalytic properties of both complexes for proton reduction were evaluated with photochemical and electrochemical studies. Two different in their nature photosensitizers, namely fluorescein and CdTe-TGA-coated quantum dots, were tested under various conditions. The role of the electron donating character of the methyl substituents was revealed in the light of the studies. Thus, catalyst 2 performs better than 1, reaching 39.1 TONs vs. 4.63 TONs in 3 h, respectively, in electrochemical experiments. In contrast, complex 1 is more photocatalytically active than 2, achieving a TON of over 6700 in 120 h of irradiation. This observed reverse catalytic activity suggests that HER mechanism follows different pathways in electrocatalysis and photocatalysis.

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