Identification of the intracellular polyhydroxyalkanoate depolymerase gene of Paracoccus denitrificans and some properties of the gene product

Paracoccus denitrificans degraded poly(3-hydroxybutyrate) (PHB) in the cells under carbon source starvation. Intracellular poly (3-hydroxyalkanoate) (PHA) depolymerase gene (phaZ) was identified near the PHA synthase gene (phaC) of P. denitrificans. Cell extract of Escherichia coli carrying lacZ-phaZ fusion gene degraded protease-treated PHB granules. Reaction products were thought to be mainly D(-)-3-hydroxybutyrate (3HB) dimer and 3HB oligomer. Diisopropylfluorophosphonate and Triton X-100 exhibited an inhibitory effect on the degradation of PHB granules. When cell extract of the recombinant E. coli was used, Mg2+ ion inhibited PHB degradation. However, the inhibitory effect by Mg2+ ion was not observed using the cell extract of P. denitrificans. (C) 2001 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.