CHEM 3050 Lecture Notes - Lecture 13: Anomer, Enol, Furanose
2 May 2018
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CHEM 3050
Lecture 13
- Takes place by ten reactions in 2 phases
- Phase 1: The Preparation
- ΔG°’: 2.1 kJ/mol per molecule of glucose, up until
the production of GAP
- Step 1: Hexokinase
- Glucose is activated by hexokinase in a Mg2+
dependent reaction that phosphorylates it to G6P
(glucose-6-phosphate) in a favorable reaction ΔG° =
-20 kJ/mol; this prevents glucose from leaving the
cell, promoting glucose uptake
Step 2: G6P Isomerase aka Phosphohexose Isomerase
• Catalyzes ene-diol rearrangement of the pyranose to a
furanose ring; the anomeric carbon is mobile in
solution, can be in equilibrium with alpha/beta
anomers both will work; The enzyme makes use of
Glu and His338 in the opening and closing of the ring.
His opens and closes the ring and Glu acts as base
and attacks proton at C2;
• The net result.. a switch in the Anomeric Carbon from
C1 to C2; The ene-diol rearrangement is normally base
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Document Summary
Takes place by ten reactions in 2 phases. G ": 2. 1 kj/mol per molecule of glucose, up until the production of gap. Glucose is activated by hexokinase in a mg2+ dependent reaction that phosphorylates it to g6p (glucose-6-phosphate) in a favorable reaction g = 20 kj/mol; this prevents glucose from leaving the cell, promoting glucose uptake. Glu and his338 in the opening and closing of the ring. His opens and closes the ring and glu acts as base and attacks proton at c2: the net result a switch in the anomeric carbon from. C1 to c2; the ene-diol rearrangement is normally base catalyzed in water, but it goes faster in enzyme g . This is the first (or second) irreversible step in glycolysis tightly regulated; it is allosterically controlled by citrate, glucose-1,6-bisphosphate and. Atp (two active sites); increased glucagon levels (high energy) decreases pfk-1 expression.
