Unknown

Dataset Information

0

Purification of porphobilinogen deaminase from Euglena gracilis and studies of its kinetics.


ABSTRACT: 1. Porphobilinogen deaminase [porphobilinogen ammonia-lyase (polymerizing), EC 4.3.1.8] from Euglena gracilis was purified more than 200-fold. 2. The enzyme has a molecular weight of 41 000 +/- 2000, does not contain a chromophoric prosthetic group, and appears not to require metal ions for activity. 3. The stoicheiometry of the overall reaction at pH 7.4 was shown to be: 4 Porphobilinogen leads to uroporphyrinogen-I + 4 NH4+. This stoicheiometry for porphobilinogen and uroporphyrinogen was also observed over a wide range of pH values. 4. Initial-velocity studies showed a hyperbolic dependence of velocity on substrate concentration, demonstrating the existence of a displacement-type mechanism. 5. Vmax. varied with pH as a typical bell-shaped curve, indicating that two ionizable groups with pK values of 6.1 and 8.9 are important for catalysis. A plot of Vmax./Km against pH showed a single ionization (pK 8.2) to influence binding of substrate.

SUBMITTER: Williams DC 

PROVIDER: S-EPMC1162603 | biostudies-other | 1981 Jan

REPOSITORIES: biostudies-other

Similar Datasets

| S-EPMC5745450 | biostudies-literature
| PRJNA734000 | ENA
| PRJNA1049904 | ENA
| PRJNA714494 | ENA
| PRJNA12796 | ENA
| PRJNA12797 | ENA
| S-EPMC1138105 | biostudies-other
| S-EPMC5683031 | biostudies-literature
| S-EPMC7403612 | biostudies-literature
| S-EPMC6366073 | biostudies-literature