Characterization of an extracellular poly(3-hydroxy-5-phenylvalerate) depolymerase from Xanthomonas sp JS']JS02

A bacterium, JS02, capable of degrading an aromatic medium-chain-length polyhydroxyalkanoate (PHA(MCL)), poly(3-hydroxy-5-phenylvalerate) (PHPV), was isolated from wastewater-treatment sludge (Ju et al. 1998), and was identified as a Xanthomonas species. An extracellular PHPV depolymerase was purified from the concentrated culture broth of Xanthomonas sp. JS02 by using a chromatography series on Sephadex G-75, QAE-Sephadex A-50 and hydroxyapatite. The molecular mass of the purified enzyme was estimated to be 41.7 kDa. The purified enzyme could hydrolyse PHPV and p-nitrophenyl (PNP)-esters of fatty acids, but did not hydrolyse short-chain-length PHAs, though the culture supernatant could hydrolyse them. The optimum pH range was 8.0-9.0 and the optimum temperature was 60 degrees C for PNP-octanoate hydrolysis. The K-m values for PNP-hexanoate and PNP-octanoate were 10.9 and 0.88 mu M, respectively.