Catalytic Mechanism of Phosphorylation and Dephosphorylation of CheY:  Kinetic Characterization of Imidazole Phosphates as Phosphodonors and the Role of Acid Catalysis†

Biochemistry ◽  
1997 ◽  
Vol 36 (48) ◽  
pp. 14965-14974 ◽  
Author(s):  
Ruth E. Silversmith ◽  
Jeryl L. Appleby ◽  
Robert B. Bourret
Keyword(s):  
Acid Catalysis ◽  
Catalytic Mechanism ◽  
Kinetic Characterization

scholarly journals Kinetic characterization of the Escherichia coli oligopeptidase A (OpdA) and the role of the Tyr607 residue

2010 ◽  
Vol 500 (2) ◽  
pp. 131-136 ◽  
Author(s):  
Ricardo Z. Lorenzon ◽  
Carlos E.L. Cunha ◽  
Marcelo F. Marcondes ◽  
Maurício F.M. Machado ◽  
Maria A. Juliano ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Kinetic Characterization

Role of Na/K/Cl cotransport in astrocytes

1992 ◽  
Vol 70 (S1) ◽  
pp. S260-S262 ◽  
Author(s):  
Wolfgang Walz
Keyword(s):  
Volume Regulation ◽  
Ion Homeostasis ◽  
Combined Cycle ◽  
Kinetic Characterization ◽  
Cultured Astrocytes ◽  
Net Uptake ◽  
Swelling Volume ◽  
External K

The kinetic characterization of the Na/K/Cl cotransport of cultured astrocytes and evidence for its involvement in volume regulation and K+ net uptake during K+ clearance are reviewed. Emphasis is put on experimental evidence for a proposed sodium cycle in astrocytes; this cycle involves a Na+–K+ ATPase that is stimulated by both a high external K+ and intracellular Na+. Elevated external K+ also stimulates the Na/K/Cl carrier, transporting these ions inward. As a result Na+ is cycled across the membrane, carried inward by the Na/K/Cl carrier, and returned by the Na+–K+ ATPase. Both functionally coupled mechanisms lead to intracellular KCl accumulation and inward movements of water to compensate for increased osmolarity. The combined cycle is expected to play a major role in the regulation of physiological K+ levels in the brain.Key words: furosemide, ion homeostasis, Na+–K+ ATPase, swelling, volume regulation.

scholarly journals Structural Characterization of an S-enantioselective Imine Reductase from Mycobacterium Smegmatis

Biomolecules ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1130
Author(s):  
Timo Meyer ◽  
Nadine Zumbrägel ◽  
Christina Geerds ◽  
Harald Gröger ◽  
Hartmut H. Niemann
Keyword(s):  
Substrate Specificity ◽  
Active Site ◽  
Mycobacterium Smegmatis ◽  
Catalytic Mechanism ◽  
Building Blocks ◽  
Secondary Amines ◽  
Hydrophobic Amino Acids ◽  
High Degree

NADPH-dependent imine reductases (IREDs) are enzymes capable of enantioselectively reducing imines to chiral secondary amines, which represent important building blocks in the chemical and pharmaceutical industry. Since their discovery in 2011, many previously unknown IREDs have been identified, biochemically and structurally characterized and categorized into families. However, the catalytic mechanism and guiding principles for substrate specificity and stereoselectivity remain disputed. Herein, we describe the crystal structure of S-IRED-Ms from Mycobacterium smegmatis together with its cofactor NADPH. S-IRED-Ms belongs to the S-enantioselective superfamily 3 (SFam3) and is the first IRED from SFam3 to be structurally described. The data presented provide further evidence for the overall high degree of structural conservation between different IREDs of various superfamilies. We discuss the role of Asp170 in catalysis and the importance of hydrophobic amino acids in the active site for stereospecificity. Moreover, a separate entrance to the active site, potentially functioning according to a gatekeeping mechanism regulating access and, therefore, substrate specificity is described.

Kinetic Characterization of Wild-Type and S229A Mutant MurB:  Evidence for the Role of Ser 229 as a General Acid†

Biochemistry ◽  
1997 ◽  
Vol 36 (4) ◽  
pp. 796-805 ◽  
Author(s):  
Timothy E. Benson ◽  
Christopher T. Walsh ◽  
Vincent Massey
Keyword(s):  
Kinetic Characterization ◽  
Wild Type ◽  
General Acid
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