The potential for utilizing biological systems as a source of biodegradable thermoplastics is becoming increasingly attractive in view of the environmental problems associated with the disposal of oil based polymers. A. eutrophus H16 and P. oleovorans are biological organisms that produce poly D-3 hydroxyalkanoates (PHAs) with interesting polymeric properties. The genes for the polymerases from these organisms have been cloned and sequenced. The present proposal seeks support to develop methods for high level expression of the polymerases. Large amounts of protein should facilitate isolation of polymerases, characterization of their substrate specificities and study of detailed reaction mechanism. A detailed understanding of biological polyester formation should allow generation of PHA analogs (polymers and copolymers) of defined composition, length and functionality.