| Popis: |
We have purified, by a three step procedure, a yeast C-nitrosoreductase and studied its action on p-nitroso-N,N-dimethylaniline. Microcalorimetric measurements performed on the microcalorimeter LKB "batch", have been given the number of protons exchanged during the reaction : four protons are involved. Two are given by NADH and the others are supplied by the buffer. We could observe two steps in the catalytic mechanism. The enthalpy change of the first one is greater than that of the second. Spectrophotometric and polarographic experiments corroborate this results : two enzymatic steps could be demonstrated. The reduction of p-nitroso-N,N-dimethylaniline is characterized by a peak with a half wave potential at -0,31 V (in M Tris-HCl, pH 8,30). While the amplitude of this one decreases, a second wave appears at -1,03 V. |
