Kinetics of inactivation

The involvement of the lysine residue present at the active site of Ehrlich ascites carcinoma (EAC) cell glyceraldehyde-3-phosphate dehydrogenase (Gra3P DH) was investigated by using the lysine specific reagents trinitrobenzenesulfonic acid (TNBS) and pyridoxal phosphate (PP). Both TNBS and PP inactivated EAC cell Gra3P DH with pseudo-first-order kinetics with the rate dependent on modifier concentration. Kinetic analysis, including a Tsou plot, indicated that both TNBS and PP apparently react with one lysine residue per enzyme molecule.

8p system191 01-06-2013 37 3   Download

The effects of divalent metal cations on structural thermostability and the inactivation kinetics of homologous class II d-xylose isomerases (XI; EC 5.3.1.5) from mesophilic (Escherichia coliand Bacillus licheniformis), thermophilic (Thermoanaerobacterium thermosulfurigenes), and hyperther-mophilic (Thermotoga neapolitana) bacteria were examined.

0p awards 06-04-2013 34 2   Download

Incubation of an NAD + -dependent succinic semialdehyde dehydrogenase from bovine brain with 4-dimethylamino-azobenzene-4-iodoacetamide (DABIA) resulted in a time-dependent loss of enzymatic activity. This inactivation followed pseudofirst-order kinetics with a second-order rate constant of 168M )1 Æmin )1 .The spectrumofDABIA-labeled enzyme showed a characteristic peak of the DABIA alkyl-ated sulfhydryl group chromophore at 436 nm, which was absent from the spectrum of the native enzyme.

0p awards 05-04-2013 31 2   Download

Inactivation of factor Va (FVa) by activated protein C (APC) is a predominant mechanism in the down-regulation of thrombin generation. In normal FVa, APC-mediated inactivation occurs after cleavage at Arg306 (with corres-pondingrate constantk¢306) or after cleavage at Arg506 (k506 ) and subsequent cleavage at Arg306 (k306). We have studied the influence of heparin on APC-catalyzed FVa inactivation by kinetic analysis of the time courses of inac-tivation. Peptide bond cleavage was identified by Western blottingusingFV-specific antibodies. ...

13p dell39 03-04-2013 41 4   Download

A complex of chagasin, a protein inhibitor fromTrypanosoma cruzi, and papain, a classic family C1 cysteine protease, has been crystallized. Kinetic studies revealed that inactivation of papain by chagasin is very fast (kon= 1.5·10 6 m )1 Æs )1 ), and results in the formation of a very tight, reversible complex (Ki =36pm), with similar or better rate and equilib-rium constants than those for cathepsins L and B.

14p vinaphone15 27-02-2013 52 2   Download