Conjugated enzymes

Overall enzyme balance and equilibrium constants are defined for the intermediate substrate and enzyme complex. The total enzyme concentration is the sum of free and conjugated enzymes with the substrates. 

The total enzyme concentration is the sum of free and conjugated enzymes with substrates. 

From the equilibrium constant, the free enzyme concentration must be defined. We know the total enzyme concentration as the sum of the conjugated enzymes with substrates and the free enzymes. 

Ubiquitin tags proteins for protein degradation. The ubiquitination requires three different enzymatic activities, a ubiquitin-activating enzyme (El), a ubiquitin-conjugating enzyme (E2 or Ubc) and a ubiquitin ligase (E3). The action of all three enzymes leads to the establishment of a poly-ubiquitin chain on target proteins which are then recognized and proteolyzed by the 26S proteasome. 

Volume 400. Phase II Conjugation Enzymes and Transport Systems Edited by Helmut Sies and Lester Packer... 

The number of sulfhydryls created on the immunoglobulin using thiolation procedures such as this one is more critical to the yield of conjugated enzyme molecules than the molar excess of maleimide-activated enzyme used in the conjugation reaction. Therefore, it is important to use a sufficient excess of Traut s reagent to obtain a sufficient number of available sulfhydryls. 

In the method shown in Figure 9A, a biotin-labeled cDNA probe is first immobilized to a polyvinylchloride microtiter plate well that is coated with bio-tinylated-bovine serum albumin [33], The target DNA is hybridized in the liquid-phase with a digoxigenin-labeled probe, so that the biotin-labeled probe can capture a marker enzyme. An antibody-conjugated enzyme is then added, followed by a chemiluminescent substrate. 

Robust decreases in the expression of the various proteasome subunits and ubiquitin-conjugating enzymes have been described in prefrontal cortex in schizophrenia. Neuronal ubiquitin and proteasomes play an important role in the assembly, function and plasticity of the synapse. Structural proteins including tubulin and a-spectrin also show decreased expression in prefrontal cortex. 

Many enzymes require additional substances in order to function effectively. Conjugated enzymes require a prosthetic group before they are catalytically active, such groups being covalently or ionically linked to the protein molecule and remaining unaltered at the end of the reaction. Catalase (EC 1.11.1.6), for instance, contains a haem group while ascorbate oxidase (EC 1.10.3.3) contains a copper atom. 

Ubiquitin-conjugating enzyme E2, catalytic domain homologs... 

Phenol is a hydrolyzed metabolite of benzene and is itself further hydrolyzed or conjugated to produce other compounds. Therefore, the toxic effects of phenol exposure may be due to a combination of the parent compound and its metabolites. The major tissues in which metabolism appears to occur are the liver, gut, lung, and kidney (Cassidy and Houston 1984 Powell et al 1974 Quebbemann and Anders 1973 Tremaine et al. 1984). Since phenol, benzene, and their major metabolites all seem to compete for the same P450 and conjugating enzymes, metabolic reactions are presumed to be saturable. 

Deng, L, Wang, C., Spencer, E., Yang, L, Braun, A., You, f., Slaughter, C., Pickart, C., and Chen, Z. J. Activation of the IkappaB kinase complex by TRAE6 requires a dimeric ubiquitin-conjugating enzyme complex and a unique polyubiquitin chain, Cdl 2000, 103, 351—361. 

Loeick, K. L., et al., RING fingers mediate ubiquitin-conjugating enzyme (E2)-dependent ubiquitination. Proc Natl Acad Sci USA, 1999, 96(20), 11364-9. 

Moynihan, T. P., et al., The ubiquitin-conjugating enzymes UbcH7 and UbcH8 interact with RING finger/IBR motif-containing domains of HHARI and H7-AP1./... 

Lisztwan, j., et al., Association of human CUL-1 and ubiquitin-conjugating enzyme CDC34 with the F-box protein p45(SKP2) evidence for evolutionary conservation in the subunit composition of the CDC34-SCF pathway. Embo J, 1998, 37/2/, 368-83. 

Hofmann, R. M. and C. M. Pickart, Noncanonical MMS2-encoded ubiquitin-conjugating enzyme functions in assembly of novel polyubiquitin chains for DNA repair. Cell, 1999, 96(5), 645-53. 

Ulrich, H. D. and S. Jentsch, Two Ring-finger proteins mediate cooperation between ubiquitin-conjugating enzymes in DNA repair. EmboJ, 2000, 19(13), 3388-97. 

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