Transferases kinetic parameters

From bisubstrate, kinetic analysis with a transferase from hen oviduct that, under the conditions of the assay, formed only GlcNAc-PP-Dol, it followed that both dolichol phosphate and UDP-GlcNAe have to he bound to the enzyme before release of the product occurs.52 However, the fact that only partially purified preparations have thus far been obtained (the preparations may also still be contaminated with substrates and product), together with experimental difficulties in handling both the substrate dolichol phosphate (which, furthermore, is not one compound, see the earlier discussion) and the unstable enzyme (enveloped in micelles of detergent), make difficult a sensible interpretation and comparison of the kinetic parameters detenuined for the different enzvme-preparations. The solubilized enzymes catalyzing reactions 1,2, and 3 have in common their alkaline pH optima and dependence on Mg2+ or Mn2+ ions. The latter fact makes (ethylenedinitrilo)tetraacetic acid (EDTA) a reversible inhibitor of enzyme activity and an important experimental tool. 

Johnson, W., Ueng, Y.-E, Widersten, M., Mannervik, B., Hayes, J. D., Sherratt, P. J., Ketterer, B., and Guengerich, F. P. (1997). Conjugation of highly reactive aflatoxin B1 exo-8,9-epoxide catalyzed by rat and human glutathione transferases Estimation of kinetic parameters. Biochemistry 36,3056-3060. 

The kinetic parameters for GBH S-transferase-catalyzed conjugation of 1-chloro-2,4-dlnltrobenzene with GSH were reported by the groups who purified fish GSH S-transferases and are sum-... 

DeLouise LA, Miller BL (2005) Enzyme immobilization in porous silicon quantitative analysis of the kinetic parameters for Glutathione-S-Transferases. Anal Chem 77 1950-1956... 

PI4K230 Al-872 <1> (<1> deletion mutant with 130000 Da compared to wild-type enzyme of 230000 Da, the enzyme is stable, 0.048 mM/mg min compared to 0.058 mM/mg min for the wild-type enzyme [39]) [39] Additional information <3> (<3> creation of a glutathione S-transferase PI4K fusion protein that is biologically active and phosphorylates phospha-tidyhnositol in ist 4-position with wortmannin sensitivity and kinetic parameters that are identical to thoses of purified wild-type enzyme [43]) [43]... 

Summary of kinetic parameters for erythrocyte transferase A using the random rapid equilibrium sequential mechanism described in the text, a is the factor by which binding of one substrate changes the affinity for the second substrate and is the ratio of maximal velocities of gly cohydrolase to transferase reactions... 

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