Characterization of a thermolabile poly(3-hydroxybutyrate) depolymerase from the marine bacterium Shewanella sp. JKCM-AJ-6, 1α. (July 2016)

• Record Type: Journal Article
• Authors: Sung, Chun-Che; Tachibana, Yuya; Kasuya, Ken-ichi
• Is Part Of: Polymer degradation and stability. Volume 129(2016:Jul.)
• Page Start: 212
• Page End: 221
• Publication Date: 2016-07
• Subjects: Thermolabile -- Halotolerant -- P(3HB) depolymerase -- Marine bacterium -- Shewanella -- Self-inhibition; Polymers -- Deterioration -- Periodicals; Stabilizing agents -- Periodicals; Polymères -- Dégradation -- Périodiques; Stabilisants -- Périodiques; 668.9
• DOI: 10.1016/j.polymdegradstab.2016.04.022
• Languages: English
• ISSNs: 0141-3910

Abstract

Abstract: A DNA fragment carrying the gene encoding poly(3-hydroxybutyrate) [P(3HB)] depolymerase was cloned from the genomic DNA of the marine bacterium Shewanella sp. strain JKCM-AJ-6, 1α (wild-type strain) from seawater. The gene was 2049 bp and encoded 683-amino acids protein with a molecular mass of 70, 382 Da. A sequence homology revealed that the deduced protein contains a signal peptide, catalytic domain (CD), fibronectin type III linker domain (LD), and two substrate-binding domains (SBDs). Meanwhile, a P(3HB) depolymerase purified from wild-type strain (wPhaZ She ) had a smaller molecular mass (47 kDa) because it lacked the SBDs, compared with calculated one based on the sequence. wPhaZ She was unstable above 15 °C and had relatively high enzymatic activity in the presence of 0.5 M NaCl, demonstrating that the enzyme is thermolabile and halotolerant. In addition, there was no decrease in the activity by self-inhibition. In contrast, a recombinant form of the enzyme (rbPhaZ She ) produced in Escherichia coli BL21 had a stronger binding affinity for P(3HB) and exhibited self-inhibition. These results demonstrate that a truncated form P(3HB) depolymerase lacking SBDs (wPhaZ She ) has an advantage for P(3HB) degradation in marine environments with relatively high NaCl concentrations owing to a less self-inhibitory effect.