Glycolysis Flashcards
Hexokinase:
Transfer of phosphoryl group to _____
Transfer of phosphoryl group facilitated by ____
C6 OH of glucose
Electrostatic catalysis
Invest 1 ATP
Phosphoglucose Isomerase
Isomerized between aldose and ketose
Glucose –> Fructose
Phosphofructokinase
Consumes 2nd ATP
Attach to C1 of fructose
Slowest reaction
Aldolase
What forms Schiff base? What is base catalyst?
Schiff base facilitates split.
Lys: forms Schiff base by Nuc attack
Asp: base catalyst (ABC)
C3/C4 split- aldehyde and ketone
Despite high positive delta G, in vivo products are substrates for the next
Triose phosphate isomerase: what does it mean to be catalytically perfect?
catalytically perfect, limited by rate of diffusion
Low barrier H bonds
Active site protein loop stabilizes transition state
pulls aldolase forward
G3P dehydrogenase
Oxidation/Phosphorylation
Aldehyde: oxidize, NAD+ reduced
Pi added to aldehyde
Covalent catalysis by CYS RESIDUE
Pulls aldolase forward
Attack by phosphate
SH of active site Cys forms covalent bond to G3P
Thioester bond
Phosphoglycerate kinase
Drive ATP formation
removal of phosphate from acyl phosphate: largeree energy
pairing = net decrease free energy
Phosphoglycerate mutase
His residue in active site- transfer of phosphoryl groups
C3 –> C2
Reversible
Enolase
What facilitates exit?
Dehydration (water released)
Mg2+ Ion coordination with C3 OH to make better leaving group
Inhibited when fluoride and Pi from complex with Mg2+ ion
Pyruvate Kinase
1) ADP attacks phosphoryl group of phosphoenolpyruvate to make ATP and enolpyruvate
2) Tautomerization (isomerization by shift of H atom) of enolpyruvate to pyruvate
Where does gluconeogensis occur?
Liver and Kidneys
Pyruvate Carboxylase
ATP/CO2 consumed
Makes 4C Oxaloacetate
Phosphoenolpyruvate Carboxykinase
GTP consumed, CO2 created
During gluconeogensis, Phosphoglycerate kinase reaction consumes ATP and NADH is used to reverse ______
G3P dehydrogenase
_______ are gluconeogenic precursors
Amino acids
Regulation step of gluconeogenesis
Fructose biphosphatase
Hydrolysis of phosphoryl group from C1
G6P – >glucose
glucose 6 phosphatase
Hydrolyzes phosphoryl group on C6
High levels of F-2,6- bip
Glycolysis
Why are amino acids (except leucine/lysine) main gluconeogenic precursors?
They can all be converted to oxaloacetate.
During starvation, proteins broken down and used to produce glucose to fuel CNS
Fatty acids can’t be converted to oxaloacetate
3C glycerol backbone of triacylglycerols is precursor
Why would cells with no gluconeogenesis have fructose biphosphatase anyway?
When fructose bisphosphate and phosphofructokinase are both active, net result in hydrolysis of ATP.
