TY - JOUR
T1 - An extracellular polyhydroxybutyrate depolymerase in Thermus thermophilus HB8
AU - Papaneophytou, Christos P.
AU - Pantazaki, Anastasia A.
AU - Kyriakidis, Dimitrios A.
PY - 2009/6
Y1 - 2009/6
N2 - The thermophilic bacterium Thermus thermophilus HB8 has been characterized as a polyhydroxybutyrate (PHB)-degrading microorganism since it grows efficiently and forms clear zones on agar plates containing PHB as sole carbon source. T. thermophilus extracellular PHB depolymerase was purified to homogeneity using an affinity chromatography protocol. The purified enzyme was estimated to have an apparent molecular mass of 42 kDa. The extracellular PHB depolymerase gene was identified as the TTHA0199 gene product of T. thermophilus HB8. The amino acid sequence of the TTHA0199 gene product shared significant homologies to other carboxylesterases. A catalytic triad was identified consisting of S183, E310, and H405. A pentapeptide sequence (GX1SX2G) exists within the molecule, characteristic for PHB depolymerases (lipase box) and for other serine hydrolases. Purified extracellular PHB depolymerase was stable at high temperatures with an optimum activity at pH 8.0. The apparent Km value of the purified enzyme for PHB was 53 μg/ml. As the main product of the enzymic hydrolysis of PHB, the monomer 3-hydroxybutyrate was identified, suggesting that the enzyme acts principally as an exo-type hydrolase.
AB - The thermophilic bacterium Thermus thermophilus HB8 has been characterized as a polyhydroxybutyrate (PHB)-degrading microorganism since it grows efficiently and forms clear zones on agar plates containing PHB as sole carbon source. T. thermophilus extracellular PHB depolymerase was purified to homogeneity using an affinity chromatography protocol. The purified enzyme was estimated to have an apparent molecular mass of 42 kDa. The extracellular PHB depolymerase gene was identified as the TTHA0199 gene product of T. thermophilus HB8. The amino acid sequence of the TTHA0199 gene product shared significant homologies to other carboxylesterases. A catalytic triad was identified consisting of S183, E310, and H405. A pentapeptide sequence (GX1SX2G) exists within the molecule, characteristic for PHB depolymerases (lipase box) and for other serine hydrolases. Purified extracellular PHB depolymerase was stable at high temperatures with an optimum activity at pH 8.0. The apparent Km value of the purified enzyme for PHB was 53 μg/ml. As the main product of the enzymic hydrolysis of PHB, the monomer 3-hydroxybutyrate was identified, suggesting that the enzyme acts principally as an exo-type hydrolase.
KW - PHB-depolymerase
KW - Poly-hydroxybutyrate (PHB)
KW - Thermus thermophilus
UR - http://www.scopus.com/inward/record.url?scp=67349188765&partnerID=8YFLogxK
U2 - 10.1007/s00253-008-1842-2
DO - 10.1007/s00253-008-1842-2
M3 - Article
C2 - 19214501
AN - SCOPUS:67349188765
SN - 0175-7598
VL - 83
SP - 659
EP - 668
JO - Applied Microbiology and Biotechnology
JF - Applied Microbiology and Biotechnology
IS - 4
ER -