Open AccessIdentification and characterization of a novel extracellular polyhydroxyalkanoate depolymerase in the complete genome sequence of Undibacterium sp. KW1 and YM2 strains
Author(s) -
Toshio Morohoshi,
Taishiro Oi,
Tomohiro Suzuki,
Shigeo Sato
Publication year - 2020
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0232698
Subject(s) - polyhydroxyalkanoates , recombinant dna , plasmid , escherichia coli , biochemistry , extracellular , chemistry , biology , linker , microbiology and biotechnology , bacteria , gene , genetics , computer science , operating system
Polyhydroxyalkanoate (PHA) is a biodegradable polymer that is synthesized by a wide range of microorganisms. One of the derivatives of PHA, poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) (PHBH) has flexible material properties and low melting temperature. We have previously demonstrated that PHBH is degradable in a freshwater environment via the formation of biofilm on the surface of the PHBH film. Undibacterium sp. KW1 and YM2, which were isolated from the biofilm present on the PHBH film in the freshwater sample, were shown to have PHBH-degrading activity. In this study, the complete genome sequence of KW1 and YM2 revealed that the extracellular PHA depolymerase gene, designated as phaZ UD , was present in their chromosomes. Sequence analysis revealed that PhaZ UD contained four domains: a signal peptide, catalytic domain, linker domain, and substrate-binding domain. Escherichia coli harboring a PhaZ UD -expressing plasmid showed PHBH-degrading activity in LB medium containing 1 wt% PHBH powder. The recombinant His-tagged PhaZ UD from KW1 and YM2 was purified from the culture supernatant and shown to have PHBH-degrading activity at the optimum temperature of 35 and 40°C, respectively. When the degradation product in the PHBH solution was treated with PhaZ UD and assayed by LC-TOF-MS, we detected various oligomer structures, but no more than pentamers, which consist of 3-hydroxybutyrate and 3-hydroxyhexanoate. These results demonstrated that PhaZ UD may have an endo-type extracellular PHA depolymerase activity.