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

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