Prostaglandins (PGs) are the oxidation products of PG endoperoxide (PGH) synthase and other tissue enzvt-nes. They occur in a tissue-specific manner and act as local hormones. Biotechnological production of PGs has been of interest, but not yet fully established. Biological tissues have been used as PG sources, but this disturbs ecological balance, and the cost of production is very high for commercial purposes. On the other hand, various microorganisms have been shown to synthesize them de novo, or biotransform precursors to active molecules, but these processes have not been further evaluated. Using mammalian enzymes in free or immobilized form is a promising new approach to synthesize PG from fatty acid substrates. Rapid enzyme inactivation during the catalysis is the main problem to be solved. Optimization of factors in the reactions and the design of special reactors that will allow removal of products continuously from the reaction medium without affecting enzyme activity need immediate attention from researchers and the pharmaceutical industry. (C) 2001 Elsevier Science Inc. All rights reserved.