Martinez_2012_Appl.Environ.Microbiol_78_6017

The obligate predator Bdellovibrio bacteriovorus HD100 shows a large set of proteases and other hydrolases as part of its hydrolytic arsenal needed for its predatory life cycle We present genetic and biochemical evidence that open reading frame ORF Bd3709 of B bacteriovorus HD100 encodes a novel medium-chain-length polyhydroxyalkanoate mcl-PHA depolymerase PhaZ(Bd) The primary structure of PhaZ(Bd) suggests that this enzyme belongs to the alpha/beta-hydrolase fold family and has a typical serine hydrolase catalytic triad serine-histidine-aspartic acid in agreement with other PHA depolymerases and lipases PhaZ(Bd) has been extracellularly produced using different hypersecretor Tol-pal mutants of Escherichia coli and Pseudomonas putida as recombinant hosts The recombinant PhaZ(Bd has been characterized and its biochemical properties have been compared to those of other PHA depolymerases The enzyme behaves as a serine hydrolase that is inhibited by phenylmethylsulfonyl fluoride It is also affected by the reducing agent dithiothreitol and nonionic detergents like Tween 80 PhaZ(Bd) is an endoexohydrolase that cleaves both large and small PHA molecules producing mainly dimers but also monomers and trimers The enzyme specifically degrades mcl-PHA and is inactive toward short-chain-length polyhydroxyalkanoates scl-PHA like polyhydroxybutyrate PHB These studies shed light on the potentiality of these predators as sources of new biocatalysts such as an mcl-PHA depolymerase for the production of enantiopure hydroxyalkanoic acids and oligomers as building blocks for the synthesis of biobased polymers.