scholarly journals Kinetic studies on the active site of pig serum .ALPHA.-glucosidase and buckwheat .ALPHA.-glucosidase.

1977 ◽  
Vol 41 (7) ◽  
pp. 1245-1248 ◽  
Author(s):  
Seiya CHIBA ◽  
Nozomu HIBI ◽  
Ken-ichi KANAYA ◽  
Tokuji SHIMOMURA
Keyword(s):  
Active Site ◽  
Kinetic Studies ◽  
Alpha Glucosidase ◽  
Pig Serum

Kinetic Studies on the Active Site of Pig Serum α-Glucosidase and Buckwheat α-Glucosidase

1977 ◽  
Vol 41 (7) ◽  
pp. 1245-1248
Author(s):  
Seiya Chiba ◽  
Nozomu Hibi ◽  
Ken-ichi Kanaya ◽  
Tokuji Shimomura
Keyword(s):  
Active Site ◽  
Kinetic Studies ◽  
Pig Serum

scholarly journals Kinetic studies and homology modeling of a dual-substrate linalool/nerolidol synthase from Plectranthus amboinicus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nur Suhanawati Ashaari ◽  
Mohd Hairul Ab. Rahim ◽  
Suriana Sabri ◽  
Kok Song Lai ◽  
Adelene Ai-Lian Song ◽  
...  
Keyword(s):  
Active Site ◽  
Catalytic Efficiency ◽  
Kinetic Studies ◽  
Homology Model ◽  
Biochemical Properties ◽  
Terpene Synthase ◽  
Monoterpene Synthase ◽  
Terminal Domain ◽  
Catalytic Active Site ◽  
Plectranthus Amboinicus

AbstractLinalool and nerolidol are terpene alcohols that occur naturally in many aromatic plants and are commonly used in food and cosmetic industries as flavors and fragrances. In plants, linalool and nerolidol are biosynthesized as a result of respective linalool synthase and nerolidol synthase, or a single linalool/nerolidol synthase. In our previous work, we have isolated a linalool/nerolidol synthase (designated as PamTps1) from a local herbal plant, Plectranthus amboinicus, and successfully demonstrated the production of linalool and nerolidol in an Escherichia coli system. In this work, the biochemical properties of PamTps1 were analyzed, and its 3D homology model with the docking positions of its substrates, geranyl pyrophosphate (C10) and farnesyl pyrophosphate (C15) in the active site were constructed. PamTps1 exhibited the highest enzymatic activity at an optimal pH and temperature of 6.5 and 30 °C, respectively, and in the presence of 20 mM magnesium as a cofactor. The Michaelis–Menten constant (Km) and catalytic efficiency (kcat/Km) values of 16.72 ± 1.32 µM and 9.57 × 10–3 µM−1 s−1, respectively, showed that PamTps1 had a higher binding affinity and specificity for GPP instead of FPP as expected for a monoterpene synthase. The PamTps1 exhibits feature of a class I terpene synthase fold that made up of α-helices architecture with N-terminal domain and catalytic C-terminal domain. Nine aromatic residues (W268, Y272, Y299, F371, Y378, Y379, F447, Y517 and Y523) outlined the hydrophobic walls of the active site cavity, whilst residues from the RRx8W motif, RxR motif, H-α1 and J-K loops formed the active site lid that shielded the highly reactive carbocationic intermediates from the solvents. The dual substrates use by PamTps1 was hypothesized to be possible due to the architecture and residues lining the catalytic site that can accommodate larger substrate (FPP) as demonstrated by the protein modelling and docking analysis. This model serves as a first glimpse into the structural insights of the PamTps1 catalytic active site as a multi-substrate linalool/nerolidol synthase.

Enzyme-coupled ultraviolet determination of alpha-amylase activity with the GEMSAEC centrifugal analyzer.

1978 ◽  
Vol 24 (9) ◽  
pp. 1620-1624 ◽  
Author(s):  
W H Porter ◽  
R E Roberts
Keyword(s):  
Linear Response ◽  
Amylase Activity ◽  
Kinetic Studies ◽  
Alpha Amylase ◽  
Coefficients Of Variation ◽  
Endogenous Glucose ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Alpha Glucosidase ◽  
As Effects

Abstract We evaluated the Harleco alpha-glucosidase/hexokinase/glucose-6-phosphate dehydrogenase-coupled alpha-amylase method, bu use of the GEMSAEC centrifugal analyzer. Performance evaluation included kinetic studies of substrate and maltose hydrolysis as well as effects of endogenous glucose and fructose. The reagent was found to give a linear response with alpha-amylase activity to greater than 1200 U/liter. Within-run precision resulted in coefficients of variation (CV) of 0.9 to 3.2% over the range studied. Day-to-day precision corresponded to CV's of 2.4 to 4.4% over the same range of alpha-amylase procedure was found to be good (r = 0.997) for patients' sera examined.

scholarly journals Synthesis and In Vitro Screening of Novel Heterocyclic β-d-Gluco- and β-d-Galactoconjugates as Butyrylcholinesterase Inhibitors

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2833
Author(s):  
Krešimir Baumann ◽  
Lorena Kordić ◽  
Marko Močibob ◽  
Goran Šinko ◽  
Srđanka Tomić
Keyword(s):  
Active Site ◽  
Kinetic Studies ◽  
Inhibitory Effect ◽  
In Vitro Screening ◽  
Sugar Moiety ◽  
Brain Barrier Permeability ◽  
The Central Nervous System ◽  
Key Residues ◽  
Micromolar Range

The development of selective butyrylcholinesterase (BChE) inhibitors may improve the treatment of Alzheimer’s disease by increasing lower synaptic levels of the neurotransmitter acetylcholine, which is hydrolysed by acetylcholinesterase, as well as by overexpressed BChE. An increase in the synaptic levels of acetylcholine leads to normal cholinergic neurotransmission and improved cognitive functions. A series of 14 novel heterocyclic β-d-gluco- and β-d-galactoconjugates were designed and screened for inhibitory activity against BChE. In the kinetic studies, 4 out of 14 compounds showed an inhibitory effect towards BChE, with benzimidazolium and 1-benzylbenzimidazolium substituted β-d-gluco- and β-d-galacto-derivatives in a 10–50 micromolar range. The analysis performed by molecular modelling indicated key residues of the BChE active site, which contributed to a higher affinity toward the selected compounds. Sugar moiety in the inhibitor should enable better blood–brain barrier permeability, and thus increase bioavailability in the central nervous system of these compounds.

scholarly journals Trinuclear copper biocatalytic center forms an active site of thiocyanate dehydrogenase

2020 ◽  
Vol 117 (10) ◽  
pp. 5280-5290 ◽  
Author(s):  
Tamara V. Tikhonova ◽  
Dimitry Y. Sorokin ◽  
Wilfred R. Hagen ◽  
Maria G. Khrenova ◽  
Gerard Muyzer ◽  
...  
Keyword(s):  
Active Site ◽  
Copper Ions ◽  
Soda Lakes ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Isosceles Triangle ◽  
Site Directed Mutagenesis ◽  
Paramagnetic Resonance ◽  
Mechanism Of Catalysis ◽  
Copper Center

Biocatalytic copper centers are generally involved in the activation and reduction of dioxygen, with only few exceptions known. Here we report the discovery and characterization of a previously undescribed copper center that forms the active site of a copper-containing enzyme thiocyanate dehydrogenase (suggested EC 1.8.2.7) that was purified from the haloalkaliphilic sulfur-oxidizing bacterium of the genus Thioalkalivibrio ubiquitous in saline alkaline soda lakes. The copper cluster is formed by three copper ions located at the corners of a near-isosceles triangle and facilitates a direct thiocyanate conversion into cyanate, elemental sulfur, and two reducing equivalents without involvement of molecular oxygen. A molecular mechanism of catalysis is suggested based on high-resolution three-dimensional structures, electron paramagnetic resonance (EPR) spectroscopy, quantum mechanics/molecular mechanics (QM/MM) simulations, kinetic studies, and the results of site-directed mutagenesis.

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