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

Abstract

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, Mg 2+ ion inhibited PHB degradation. However, the inhibitory effect by Mg 2+ ion was not observed using the cell extract of P. denitrificans.