The broad objective of this study is to uncover the control of heme and porphyrin synthesis. The approach to be used is to elucidate the structure-function relationship and the mechanism of each of the enzymes concerned in the early steps of porphyrin synthesis. This particular project will concentrate on the enzyme, porphobilinogen synthase, an octameric enzyme which catalysis the synthesis of the pyrrole, porphobilinogen, from two molecules of sigma-aminolevulinic acid. The research will be concerned with subunit-interaction, determination of the primary structure of the enzyme and determination of the amino acid residue involved at the active site.