Selective covalent labeling with radiolabeled suicide substrates for isolating P450s

An outlook on suicide enzyme inhibition and drug design

There have been recent renewed interests in the importance of suicide enzyme inhibition. The principal objective of this review is to investigate all types of suicide inhibitions for natural enzymes, artificial biocatalysts as well as therapeutic potential of enzyme suicide inhibition. It is discussed the suicide inhibition beneficial in drug design and treatments and non-beneficial achievements for some industrial enzymes such as HRP peroxidase enzyme. The design of biomimetic artificial enzymes explained to prevent inhibition by protecting the active site via environmental conditions. Suicide enzyme inhibition development can be the key mechanism against sever diseases such as SARS. In this report, suicide enzyme inactivation classes are classified based on target enzyme groups via their substrates.

Bioinformatic and enzymatic characterization of the MAPEG superfamily

The membrane associated proteins in eicosanoid and glutathione metabolism (MAPEG) superfamily includes structurally related membrane proteins with diverse functions of widespread origin. A total of 136 proteins belonging to the MAPEG superfamily were found in database and genome screenings. The members were found in prokaryotes and eukaryotes, but not in any archaeal organism. Multiple sequence alignments and calculations of evolutionary trees revealed a clear subdivision of the eukaryotic MAPEG members, corresponding to the six families of microsomal glutathione transferases (MGST) 1, 2 and 3, leukotriene C4 synthase (LTC4), 5-lipoxygenase activating protein (FLAP), and prostaglandin E synthase. Prokaryotes contain at least two distinct potential ancestral subfamilies, of which one is unique, whereas the other most closely resembles enzymes that belong to the MGST2/FLAP/LTC4 synthase families. The insect members are most similar to MGST1/prostaglandin E synthase. With the new data available, we observe that fish enzymes are present in all six families, showing an early origin for MAPEG family differentiation. Thus, the evolutionary origins and relationships of the MAPEG superfamily can be defined, including distinct sequence patterns characteristic for each of the subfamilies. We have further investigated and functionally characterized representative gene products from Escherichia coli, Synechocystis sp., Arabidopsis thaliana and Drosophila melanogaster, and the fish liver enzyme, purified from pike (Esox lucius). Protein overexpression and enzyme activity analysis demonstrated that all proteins catalyzed the conjugation of 1-chloro-2,4-dinitrobenzene with reduced glutathione. The E. coli protein displayed glutathione transferase activity of 0.11 micromol.min(-1).mg(-1) in the membrane fraction from bacteria overexpressing the protein. Partial purification of the Synechocystis sp. protein yielded an enzyme of the expected molecular mass and an N-terminal amino acid sequence that was at least 50% pure, with a specific activity towards 1-chloro-2,4-dinitrobenzene of 11 micromol.min(-1).mg(-1). Yeast microsomes expressing the Arabidopsis enzyme showed an activity of 0.02 micromol.min(-1).mg(-1), whereas the Drosophila enzyme expressed in E. coli was highly active at 3.6 micromol.min(-1).mg(-1). The purified pike enzyme is the most active MGST described so far with a specific activity of 285 micromol.min(-1).mg(-1). Drosophila and pike enzymes also displayed glutathione peroxidase activity towards cumene hydroperoxide (0.4 and 2.2 micromol.min(-1).mg(-1), respectively). Glutathione transferase activity can thus be regarded as a common denominator for a majority of MAPEG members throughout the kingdoms of life whereas glutathione peroxidase activity occurs in representatives from the MGST1, 2 and 3 and PGES subfamilies.