Biochemical and functional characterization of a periplasmic disulfide oxidoreductase from Neisseria meningitidis essential for meningococcal viability.

TlpAs (thioredoxin-like proteins) are bacterial thioredoxin-like periplasmic disulfide oxidoreductases generally involved in cytochrome c maturation (Ccm) process. They contain a characteristic CXXC active site motif involved in disulfide exchange reaction. In the human pathogenic Neisseria meningitidis species, no TlpA has been characterized so far.

Evidence that glutathione and the glutathione system efficiently recycle 1-cys sulfiredoxin in vivo.

Aims: Typical 2-Cys peroxiredoxins (2-Cys Prxs) are Cys peroxidases that undergo inactivation by hyperoxidation of the catalytic Cys, a modification reversed by ATP-dependent reduction by sulfiredoxin (Srx). Such an attribute is thought to provide regulation of 2-Cys Prxs functions. The initial steps of the Srx catalytic mechanism lead to a Prx/Srx thiolsulfinate intermediate that must be reduced to regenerate Srx.

Methionine sulfoxide reductase: chemistry, substrate binding, recycling process and oxidase activity.

Three classes of methionine sulfoxide reductases are known: MsrA and MsrB which are implicated stereo-selectively in the repair of protein oxidized on their methionine residues; and fRMsr, discovered more recently, which binds and reduces selectively free L-Met-R-O. It is now well established that the chemical mechanism of the reductase step passes through formation of a sulfenic acid intermediate. The oxidized catalytic cysteine can then be recycled by either Trx when a recycling cysteine is operative or a reductant like glutathione in the absence of recycling cysteine which is the case for 30% of the MsrBs.

Kinetic evidence that methionine sulfoxide reductase A can reveal its oxidase activity in the presence of thioredoxin.

The mouse methionine sulfoxide reductase A (MsrA) belongs to the subclass of MsrAs with one catalytic and two recycling Cys corresponding to Cys51, Cys198 and Cys206 in Escherichia coli MsrA, respectively. It was previously shown that in the absence of thioredoxin, the mouse and the E. coli MsrAs, which reduce two mol of methionine-O substrate per mol of enzyme, displays an in vitro S-stereospecific methionine oxidase activity.

An unusual effect of NADP+ on the thermostability of the nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase from Streptococcus mutans.

Adiabatic differential scanning calorimetry was used to investigate the effect of NADP+ on the irreversible thermal denaturation of the nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPN) from Streptococcus mutans. The GAPN-NADP+ binary complex showed a strongly decreased thermal stability, with a difference of about 20 °C between the temperatures of the thermal transition peak maxima of the complex and the free protein. This finding was similar to the previously described thermal destabilization of GAPN upon binding of inorganic phosphate to the substrate binding site and can be interpreted as the shift of the equilibrium between 2 conformers of tetrameric GAPN upon addition of the coenzyme.