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1,638 results on '"Borchardt, Ronald T."'

17. Comparative kinetics of cofactor association and dissociation for the human and trypanosomal S-adenosylhomocysteine hydrolases. 1. Basic features of the association and dissociation process

Author

Qing-Shan Li, Sumin Cai, Borchardt, Ronald T., Jianwen Fang, Kuczera, Kryzysztof, Middaugh, Russell C., and Schowen, Richard L.

Subjects
Dissociation -- Research, Homocysteine -- Chemical properties, Homocysteine -- Structure, Hydrolases -- Chemical properties, Hydrolases -- Structure, Enzymes -- Chemical properties, Enzymes -- Structure, Biological sciences, Chemistry
Abstract

A study was conducted to show that the equilibrium and kinetic properties of association and dissociation of the cofactor by Hs-SAHH and Tc-SAHH are qualitatively similar. Both enzymes exhibit the dimer of dimers structure in which the homotetramer is made up of two pairs of monomers and within each pair of monomers, a C-terminal segment from each partner penetrates into the other partner subunit and forms part of the cofactor binding site.

Published
2007

19. Effects of ligand binding and oxidation on hinge-bending motions in S-adenosyl-L-homocysteine hydrolase

Author

Mengmeng Wang, Unruh, Jay R., Johnson, Carey K., Kuczera, Krzysztof, Schowen, Richard L., and Borchardt, Ronald T.

Subjects
Ligand binding (Biochemistry) -- Research, Homocysteine -- Structure, Homocysteine -- Research, Biological sciences, Chemistry
Abstract

Fluorescence anisotropy decay studies are performed to follow the structure and dynamics of S-adenosyl-L-homocysteine(AdoHcy) hydrolase in its catalytic cycle. Results indicate that AdoHcy hydrolase exists in an equilibrium between open and closed structures, with the equilibrium shifted toward the open form for the substrate-free enzyme and towards the closed form in the presence of substrates /analogues.

Published
2006

29. Contributions of active site residues to the partial and overall catalytic activities of human S-adenosylhomocysteine hydrolase

Author

Elrod, Philip, Zhang, Jinsong, Yang, Xiaoda, Yin, Dan, Hu, Yongbo, Borchardt, Ronald T., and Schowen, Richard L.

Subjects
Enzymes -- Structure-activity relationship, Amino acids -- Structure-activity relationships, Catalysis -- Analysis, Binding sites (Biochemistry) -- Analysis, Biological sciences, Chemistry
Abstract

Research elucidates the primary, secondary/tertiary, and quaternary structure and functional aspects such as catalytic activities of the mutant enzymes, each containing alanine substitution for each of the five residues involved in the active site of the human S-adenosylhomocysteine hydrolase.

Published
2002

35. Computational characterization of substrate binding and catalysis in S-adenosylhomocysteine hydrolase

Author

Hu, Yongbo, Yang, Xiaoda, Yin, Daniel H., Mahadevan, Janaki, Kuczera, Krzysztof, Schowen, Richard L., and Borchardt, Ronald T.

Subjects
Biochemistry -- Research, Adenosine -- Physiological aspects, Hydrolysis -- Physiological aspects, Homocysteine -- Physiological aspects, Biological sciences, Chemistry
Abstract

Research has been conducted on the S-adenosylhomocysteine hydrolase which catalyzes the AdoHcy reversible hydrolysis to adenosine and homocysteine. The binding of the natural substrates during the catalysis has been investigated via the computational docking program AutoDock and the results are discussed.

Published
2001

37. Mechanisms of inactivation of human S-adenosylhomocysteine hydrolase by 5',5',6',6',-tetradehydro-6'-deoxy-6'-halohomoadenosines

Author

Yang, Xiaoda, Yin, Dan, Wnuk, Stanislaw F., Robins, Morris J., and Borchardt, Ronald T.

Subjects
Enzyme inhibitors -- Research, Hydrolysis -- Research, Biological sciences, Chemistry
Abstract

Only 5',5',6',6'-tetradehydro-6'-deoxy-6'iodohomoadenosine completely inhibits human S-adenosylhomocysteine hydrolase in a mechanism similar to the acetylenic analogue of adenosine. Four moles of the inhibitor bound to the tetrameric enzyme, converting 2 equiv of E-NAD+ to E-NADH and releasing 2 equiv of E-NAD+ into solution.

Published
2000

38. Substrate binding stabilizes S-adenosylhomocysteine hydrolase in a closed conformation

Author

Yin, Dan, Yang, Xiaoda, Hu, Yongbo, Kuczera, Krysztof, Schowen, Richard L., Borchardt, Ronald T., and Squier, Thomas C.

Subjects
Cytochemistry -- Research, Homocysteine -- Physiological aspects, Catalysis -- Physiological aspects, Anisotropy -- Physiological aspects, Binding sites (Biochemistry) -- Physiological aspects, Biological sciences, Chemistry
Abstract

Substrate binding has been studied and found to stabilize S-adenosylhomocysteine hydrolase in a closed conformation. Crystal structures of the hydrolase in the substrate-free HNAD+ form and a substrate bound NADH form were compared. Large differences were seen in the spatial arrangement of the catalytic and NAD+ binding domains. The catalytic and NAD+ binding domains form a closed active site through interactions with the substrate before substrate oxidation.

Published
2000

39. Evidence for the involvement of histidine A(12) in the aggregation and precipitation of human relaxin induced by metal-catalyzed oxidation

Author

Khossravi, Mehrnaz, Shire, Steven J., and Borchardt, Ronald T.

Subjects
Biochemistry -- Research, Histidine -- Research, Relaxin -- Research, Oxidation-reduction reaction -- Analysis, Catalysis -- Analysis, Amino acids -- Research, Biological sciences, Chemistry
Abstract

Research has been conducted on the metal-catalyzed oxidation of the recombinant human relaxin. The oxidation of His A(12) amino acid has been carried out.

Published
2000

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