INSTITUTE OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF BIOTECHNOLOGY
PROTEIN AND ENZYME ENGINEERING
TOPIC:GLUCOISOMERASE
PRESENTED BY: AKSHAY MISHRA
ROLL NO: 201411029009
BUNDELKHAND UNIVERSITY, JHANSI

INTRODUCTION TO GLUCOISOMERASE:
• The other name for glucose isomerase are D-xylose ketol isomerase, xylose
isomerase (XI), xylose keto isomerase, and xylose ketol-isomerase.
• This enzyme is an intramolecular oxidoreductase that can interconvert
aldoses and ketoses.
• Glucose isomerase reversibly isomerizes D-glucose and D-xylose to D-
fructose and D-xylulose, respectively.
• It is one of the three most commonly produced industrial enzymes, along
with amylase and protease.

ENZYME NOMENCLATURE:
• IUBMB ENTRY – EC 5.3.1.5
• SYSTEMATIC NAME of this enzyme class is D-xylose aldose-ketose-isomerase.
• This enzyme belongs to the family of isomerases.

FUNCTION:
• Catalyze the reversible isomerization of D-glucose and D-xylose to D-fructose and
D-xylulose, respectively.
• Exhibits activity against a broad spectrum of sugar of 12 substrates, including D-
ribose, L-rhamnulose, L-arabinose, and D-allose, although the substrate specificity
of GIs can vary depending on the source strain or organism.
• GI is known to exhibit the highest activity in the presence of divalent metal ions
such as Mg2+, Mn2+, and Co2+ while inhibitor as xylitol, mannitol etc.
• Efficiently perform at ph 7 to 9 and temperature of 60 to 80 degrees Celcius.

REACTION MECHANISM:
• The catalytic reaction of GI occurs in three major steps: (i) ring opening, (ii)
isomerization, and (iii) ring closure.
• An open ring state, and a closed ring form product is created after isomerization via a
hydride shift.

Figure: Isomerization mechanism of GI. (a) Three major steps
are involved in the configuration change from D-glucose to D-
fructose catalyzed by GI. (b) Hydride shift mechanism of GI.

STRUCTURE:
• GI consists of a TIM barrel-like domain and an extended α-helix domain
(Figure A, B) which are assembled into a functional tetramer (Figure C) .
The substrate-binding pocket is formed by two protomers and the GI
active site is located on the TIM barrel fold (Figure C). The GI exists as a
tetramer with 222 crystallographic symmetry and includes four active sites
for substrate isomerization.
• The typical GI active site contains two sites, M1 and M2, for metal binding.

Crystal structure of the GI from Streptomyces rubiginosus
(SruGI). (a) GI protomer consists of a TIM-barrel domain and an
extended α-helical domain. (b) The extended α-helical domain
interacts with the TIM barrel domain from the neighboring GI
molecule. (c) Tetrameric GI shows 222 symmetry.

SOURCE ORGANISMS OF GI:
• Streptomyces griseofuscus
• Streptomyces murinus (SmGI)
• Thermus caldophilus
• Thermotoga neapolitana

APPLICATION OF GI:
• GI plays an important role in sugar metabolism, fulfilling nutritional requirements
in bacteria.
• GI is an important industrial enzyme for the production of high-fructose corn
syrup(HFCS) and bioethanol.
• Products containing Xylose-Isomerase are sold as over-the-counter dietary
supplements to combat fructose malabsorption, primarily in Europe and under
brand names including Fructaid, Fructease and Fructosin.
• GIs can also produce rare sugars that are used in food or medicinal products.

REFERENCES:
• MDPI review by Ki Hyun Nam
• Wikipedia
• PubMed

THANK YOU