Glutathione titration

Lewis, S.D., Misra, D.C. and Shafer, J.A. (1980) Determination of interactive thiol ionizations in bovine serum albumin, glutathione, and other thiols by potentiometric difference titration. Biochemistry, 19, 6129-6180. 

Glutathione related isopeptides of general structure (y-Glu-Cys) -Gly Size-quantized CdS formed by sulfide-ion titration... 

Unusual features of vitamin Bn observed by some investigators include (1) the cyanide group is an artifact of preparation (2) the only vitamin synthesized in appreciable amounts only by microorganisms (possible in tumors) (3) only vitamin with a metal ion (4) works with glutathione (5) glutathione content decreased on B12 deficiency (6) mitosis retarded in B12 deficiency (7) requires intrinsic factor (enzyme) for oral activity (8) increases tumor size (Rous sarcoma) (9) diamagnetic properties (10) no acidic or basic groups revealed on titration (no pKa). 

The formation of mixed enzyme-CoA or enzyme-acyl carrier protein disulfides was supported by the fact that the activation by these compounds was readily reversed by treatment with glutathione or cysteine (49). Preliminary experiments (50) with radioactive CoA or by titration of sulfhydryl groups in the protein suggest that maximum activation is associated with the incorporation of 4 equivalents of CoA per mole of protein (one per subunit). 

FiO. 11. Ckwnplex formation between the 2-electron-reduced (EHi) form of E. coli glutathione reductase and NADPH. EH2 was produced by anaerobic reduction with borohydride time was allowed for the slight excess of borohydride to react with water before beginning the titration with NADPH. 1, Oxidized 2, EHi 3, EHa-f-0.45 equivalent NADPH 4, EHi-1-0.90 equivalent NADPH and 5, EH -1-2.75 equivalents NADPH. 

Figure 8. Renaturation of low molecular weight urokinase observed in samples collected from continuous flow refolding. UK was injected in 9.3 M urea into 2.0 M urea, 20 mM Bis-Tris, pH 7.8 buffer with a gradient from 2.5 mM reduced glut-athione (GSH) to 2.5 mM oxidized glutathione (GSSG). Upper panel Data for GSSG concen-tration are from direct absorbance measurements at the secondary UV detector data for GSH were determined by DTNB titration of collected fractions. Lower panel urokinase activity in collected fractions measured by spectrophotometric assay using S-2444 (12) in a Molecular Devices titerplate reader.

Procedure 7.3 Spectrophotometric Titration of PC2 and Glutathione with Cadmium(ll) and Copper(ll)... 

Siegmund and Korber 101 described the spectrophotometric titration of penicillin with p-chloromercuribenzoate after its cleavage by penicillinase. The thiazolidine moiety reacts with excess mercuribenzoate. After 30 minutes the excess is titrated with a solution of cysteine or glutathione. The endpoint is determined by measuring the absorbance at 250 nm. As little as 0.1 xM of penicillin can be determined. Preparation of a stable p-chloromercuribenzoate... 

The normal catalytic process involves the sequence I- -II->-III->-IV- -I, while the steps IV- V- -VI- -III may also be part of the overall reaction. Thelander (131) has pointed out that the reaction mechanism of thioredoxin reductase differs from those of glutathione reductase and lipoyldehydrogenase because during the anaerobic titration of thioredoxin reductase no flavin semiquinone intermediate could be detected. Although thioredoxin reductase contains two subunits only one octapeptide... 

See also - Table 5.1, Genetic Code, Glutathione, Metabolism of Serine, Glycine, and Threonine, Essential Amino Acids, Titration Curve of Glycine... 

---