Substrate specificity of a recombinant D-lyxose isomerase from Serratia proteamaculans that produces D-lyxose and D-mannose.
OBJECTIVE
Characterization of substrate specificity of a D-lyxose isomerase from Serratia proteamaculans and application of the enzyme in the production of D-lyxose and D-mannose.


RESULTS
The concentrations of monosaccharides were determined using a Bio-LC system. The activity of the recombinant protein from Ser. proteamaculans was the highest for D-lyxose among aldoses, indicating that it is a D-lyxose isomerase. The native recombinant enzyme existed as a 54-kDa dimer, and the maximal activity for D-lyxose isomerization was observed at pH 7.5 and 40 degrees C in the presence of 1 mmol l(-1) Mn(2+). The K(m) values for D-lyxose, D-mannose, D-xylulose, and D-fructose were 13.3, 32.2, 3.83, and 19.4 mmol l(-1), respectively. In 2 ml of reaction volume at pH 7.5 and 35 degrees C, D-lyxose was produced at 35% (w/v) from 50% (w/v) D-xylulose by the D-lyxose isomerase in 3 h, while D-mannose were produced at 10% (w/v) from 50% (w/v) D-fructose in 5 h.


CONCLUSIONS
We identified the putative sugar isomerase from Ser. proteamaculans as a D-lyxose isomerase. The enzyme exhibited isomerization activity for aldose substrates with the C2 and C3 hydroxyl groups in the left-hand configuration. High production rates of d-lyxose and d-mannose by the enzyme were obtained.


CONCLUSIONS
A new D-lyxose isomerase was found, and this enzyme had higher activity for D-lyxose and D-mannose than previously reported enzymes. Thus, the enzyme can be applied in industrial production of D-lyxose and D-mannose.
Park
C-S
CS
Department of Bioscience and Biotechnology, Konkuk University, Seoul, Korea.
Yeom
S-J
SJ
Lim
Y-R
YR
Kim
Y-S
YS
Oh
D-K
DK
D019747:Aldose-Ketose Isomerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008358:Mannose / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010429:Pentoses / Q000378:metabolism*; D055503:Protein Multimerization; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012705:Serratia / Q000201:enzymology*; D013379:Substrate Specificity; D013696:Temperature
D004269:DNA, Bacterial; D010429:Pentoses; D011994:Recombinant Proteins; C043333:lyxose; D019747:Aldose-Ketose Isomerases; C021525:D-lyxose ketol-isomerase; D008358:Mannose