title: A highly active phosphoglucomutase from Clostridium thermocellum: cloning, purification, characterization and enhanced thermostability.
abstract: OBJECTIVE
  Discovery and utilization of highly active and thermostable phosphoglucomutase (PGM) would be vital for biocatalysis mediated by multiple enzymes, for example, high-yield production of enzymatic hydrogen.
  
  
  RESULTS
  The thermophilic cellulolytic bacterium Clostridium thermocellum was hypothesized to have a very active PGM because of its key role in microbial cellulose utilization. The Cl. thermocellum ORF Cthe1265 encoding a putative PGM was cloned and expressed in Escherichia coli. The purified enzyme appeared to be a monomer with an estimated molecular weight of 64.9 kDa. This enzyme was found to be a dual-specificity enzyme - PGM/phosphomannomutase (PMM). Mg(2+) and Mn(2+) were activators. Ser144 was identified as an essential catalytic residue through site-directed mutagenesis. The k(cat) and K(m) of PGM were 190 s(-1) and 0.41 mmol l(-1) on glucose-1-phosphate and 59 s(-1) and 0.44 mmol l(-1) on mannose-1-phosphate, respectively, at 60 degrees C. Thermostability of PGM at a low concentration (2 nmol l(-1), 100 U l(-1)) was enhanced by 12-fold (i.e. t(1/2) = 72 h) at 60 degrees C with addition of bovine serum albumin, Triton X-100, Mg(2+)and Mn(2+).
  
  
  CONCLUSIONS
  The ORF Cthe1265 was confirmed to encode a PGM with PMM activity. This enzyme was the most active PGM reported.
  
  
  CONCLUSIONS
  This highly active PGM with enhanced thermostability would be an important building block for in vitro synthetic biology projects (complicated biotransformation mediated by multiple enzymes in one pot).
authors: Biological Systems Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
authors: Y
authors: Y
authors: Wang
authors: Y-H P
authors: YH
authors: Zhang
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D003001:Cloning, Molecular; D048013:Acetivibrio thermocellus / Q000201:enzymology* / Q000235:genetics; D004795:Enzyme Stability; D006358:Hot Temperature; D007700:Kinetics; D010733:Phosphoglucomutase / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D010733:Phosphoglucomutase