A novel superfamily designated MAPEG (Membrane
Associated Proteins in Eicosanoid and Glutathione metabolism),
including members of widespread origin with diversified
biological functions is defined according to enzymatic
activities, sequence motifs, and structural properties.
Two of the members are crucial for leukotriene biosynthesis,
and three are cytoprotective exhibiting glutathione S-transferase
and peroxidase activities. Expression of the most recently
recognized member is strongly induced by p53, and may therefore
play a role in apoptosis or cancer development. In spite
of the different biological functions, all six proteins
demonstrate common structural characteristics typical of
membrane proteins. In addition, homologues are identified
in plants, fungi, and bacteria, demonstrating this superfamily
to be generally occurring.