Glucose Isomerase Production of High-Fructose Syrups

Antrim, Richard L.; Colilla, William; Schnyder, B. J.

doi:10.1016/b978-0-12-041102-3.50010-9

Cited by 52 publications

(30 citation statements)

References 63 publications

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“…Besides the inherent value in understanding the genetic organization and regulation of the xylose degradation genes in Streptomyces spp., it should also be noted that xylose isomerase is an extremely important industrial enzyme (1). Because xylose isomerase is also capable of catalyzing the conversion of glucose to the sweeter sugar fructose, tons of microbial xylose isomerases are used each year in the commercial conversion of starch to high-fructose syrups.…”

Section: Discussionmentioning

confidence: 99%

Genetic organization and regulation of the xylose degradation genes in Streptomyces rubiginosus

Wong¹,

Ting²,

Lin³

et al. 1991

J Bacteriol

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The xylose isomerase (xylA) and the xylulose kinase (xylB) genes from Streptomyces rubiginosus were isolated, and their nucleotide sequences were determined. The xylA and xylB genes encode proteins of 388 and 481 amino acids, respectively. These two genes are transcribed divergently from within a 114-nucleotide sequence separating the coding regions. Regulation of the xyl genes in S. rubiginosus was examined by fusing their promoters to the Pseudomonas putida catechol dioxygenase gene and integrating the fusions into the minicircle integration site on the S. rubiginosus chromosome. The expression of catechol dioxygenase was then measured under a variety of conditions. The results indicated that transcription of the xyl genes was induced by D-xylose and repressed by glucose. Data from quantitative S1 mapping were consistent with this conclusion and suggested that xylA had one and xylB had two transcription initiation sites. The transcription initiation site of xylA was 40 bp upstream of the coding region. The two transcription initiation sites of xylB were 20 and 41 bp 5' of its translation initiation codon. Under control of appropriate regulatory elements, the cloned xyl genes are capable of complementing either Escherichia coli xylose isomerase- or xylulose kinase-deficient strains. The deduced amino acid sequence of the S. rubiginosus xylA protein is highly homologous to sequences of other microbial xylose isomerases.

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Section: Discussionmentioning

confidence: 99%

Genetic organization and regulation of the xylose degradation genes in Streptomyces rubiginosus

Wong¹,

Ting²,

Lin³

et al. 1991

J Bacteriol

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“…[5][6][7][8][9][10] The most important industrial method for fructose production is by the enzymatic isomerization of glucose syrup, a process yielding only about 50 % fructose. [11] Direct conversion of the obtained aqueous glucose/fructose mixture would be problematical since the dehydration in water suffers from side reactions by which HMF is rehydrated to leuvulinic acid and formic acid. [12] In order to find an economical and environmentally feasible industrial process for the production of HMF, an efficient direct conversion from glucose would therefore be most beneficial.…”

Section: Introductionmentioning

confidence: 99%

Metal‐Free Dehydration of Glucose to 5‐(Hydroxymethyl)furfural in Ionic Liquids with Boric Acid as a Promoter

Ståhlberg

Rodríguez-Rodríguez

Fristrup

et al. 2011

Chemistry A European J

191

139

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The dehydration of glucose and other hexose carbohydrates to 5-(hydroxymethyl)furfural (HMF) was investigated in imidazolium-based ionic liquids with boric acid as a promoter. A yield of up to 42% from glucose and as much as 66% from sucrose was obtained. The yield of HMF decreased as the concentration of boric acid exceeded one equivalent, most likely as a consequence of stronger fructose-borate chelate complexes being formed. Computational modeling with DFT calculations confirmed that the formation of 1:1 glucose-borate complexes facilitated the conversion pathway from glucose to fructose. Deuterium-labeling studies elucidated that the isomerization proceeded via an ene-diol mechanism, which is different to that of the enzyme-catalyzed isomerization of glucose to fructose. The introduced non-metal system containing boric acid provides a new direction in the search for catalyst systems allowing efficient HMF formation from biorenewable sources.

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“…This enzyme also catalyzes the conversion of D-glucose to D-fructose in vitro and has been used as an industrial biocatalyst for production of high fructose corn syrup (13). Xylose isomerase displays lower kcat and higher Km values for glucose than those for xylose, and it requires different metal ions for enzyme catalysis on these substrates (i.e., Mn2+ for xylose and Co2+ for glucose) (14)(15)(16).…”

mentioning

confidence: 99%

Switching substrate preference of thermophilic xylose isomerase from D-xylose to D-glucose by redesigning the substrate binding pocket.

Meng

Lee

Bagdasarian

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

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The substrate specificity of thermophilic xylose isomerase from Clostridium thenmosulfurogenes was examined by using predictions from the known crystal structure of the Arthrobacter enzyme and site-directed mutagenesis of the thermophilexylA gene. The orientation ofglucose as a substrate in the active site of the thermophilic enzyme was modeled to position the C-6 end of hexose toward His-101 in the substratebinding pocket. The locations of which (kCt/Kl,) for glucose than the wild-type enzyme of 5-and 2-fold, respectively. They also exhibited 1.5-and 3-fold higher catalytic efficiency for D-glucose than for D-xylose, respectively. These results provide evidence that alteration in substrate specificity of factitious thermophilic xylose isomerases can be achieved by designing reduced steric constraints and enhanced hydrogenbonding capacity for glucose in the substrate-binding pocket of the active site.Specificity of enzymes toward their substrates is determined in part by molecular residues that provide for binding of the substrate and that maintain substrate steric configuration in the active site. A variety of factors influence enzymesubstrate complementarity and catalytic efficiency including steric fit, charge interactions, hydrogen bonding, and hydrophobic interactions (1). Until recently, the main strategy to reveal and study the molecular basis of these factors was to determine the tertiary structure of the enzyme-substrate complexes by x-ray crystallography. Redesigning proteins by engineering of their genes is now a viable approach that complements structural studies and enables determination of amino acid substitution effects on mutant enzyme function. Thus, substrate specificity has been altered by redesigning the structural frame of an enzyme (1-4), its electrostatic network (5-8), or its hydrophobic interaction with the substrate (9). Catalytic function of an enzyme can also be changed and regulated by modifications of the physical microenvironment of its catalytic site (10, 11).Xylose isomerase (D-xylose ketol-isomerase; EC 5.3.1.5) converts D-xylose to D-xylulose during xylose metabolism in various microorganisms (12). This enzyme also catalyzes the conversion of D-glucose to D-fructose in vitro and has been used as an industrial biocatalyst for production of high fructose corn syrup (13). Xylose isomerase displays lower kcat and higher Km values for glucose than those for xylose, and it requires different metal ions for enzyme catalysis on these substrates (i.e., Mn2+ for xylose and Co2+ for glucose) (14-16).The catalytic mechanism for xylose isomerase was originally believed to involve histidine-directed general base catalysis (17). Currently, an alternative mechanism of catalysis has been proposed based on results of x-ray crystallographic studies on Arthrobacter or Streptomyces enzymes (18-21) and biochemical properties exhibited by thermophilic enzymes obtained by site-directed mutagenesis of the xylA gene from Clostridium thermosulfurogenes (22).The enzymatic interconversion of...

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Glucose Isomerase Production of High-Fructose Syrups

Cited by 52 publications

References 63 publications

Genetic organization and regulation of the xylose degradation genes in Streptomyces rubiginosus

Genetic organization and regulation of the xylose degradation genes in Streptomyces rubiginosus

Metal‐Free Dehydration of Glucose to 5‐(Hydroxymethyl)furfural in Ionic Liquids with Boric Acid as a Promoter

Switching substrate preference of thermophilic xylose isomerase from D-xylose to D-glucose by redesigning the substrate binding pocket.

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