glycolysis Flashcards
differences between hexokinase and glucokinase
hexokinase- most tissues, can phosphorylate any 6C sugar, low Km/Vmax, inhibited by glucose-6-P
glucokianse- only in liver and pancreatic b-cells, high Km, limited to glucose, NOT inhibited by glucose-6-P
irreversible steps of glycolysis
1,3,10
required cofactor for hexokinase and glucokinase
both require Mg2+ bc it forms a complex with ATP (needed for adding P)
rate limiting step of glycolysis
step 3- conversion of fructose-6-P to fructose-1,6-bisphosphate by phosphofructokinase-1
2 enzymes capable of converting DHAP to G3P
triose phosphate isomerase
glycerol phosphate dehydrogenase
what substances can act on glyceraldehyde-3-P dehydrogenase to uncouple oxidate and phsophorylation?
Arsenate
mercury
ROS
what is unique about the run catalyzed by glyceraldehyde-3-phosphate dehydrogenase?
adds Pi (instead of ATP) to form high energy phosphate bond via thirster mechanism
which enzymes catalyze the 2 substrate level phosphorylations in glycolysis?
3-phosphoglycerate kinase
pyruvate kinase
which aa is made from the transamination of pyruvate?
alanine
which aa can be formed from 3-phosphoglycerate?
serine, glycine, cysteine
which glycolytic intermediates are used to made ribose-5-P? (3)
- fructose-6-P
- glucose-6-P
- glyceraldehyde-3-P
which substances provides a glycolysis “detour”?
2,3-bisphosphoglycerate
allosteric controllers of phosphofructokinase-1
activator- AMP, fructose-2,6-bisphosphate
inhibitor- ATP
regulation of hexokinase
inhibitor: glucose-6-P
regulation of glucokinase
inhibitor: GKRP (active when fructose-6-P levels are high and inactive when glucose levels are high)
regulation of pyruvate kinase
inhibitors: ATP, alanine, PKA/glucagon
activators: protein phosphatase/insulin, fructose-1,6-bisphosphate
what is the pasteur effect?
when lots of O2 present, unnecessary to breakdown every molecule of glucose via glycolysis because of the greater efficiency of TCA/ETC. more aerobic conditions = greater inhibition of glycolysis
m/c inherited enzyme deficiency in glycolysis
pyruvate kinase (95%)
consequences of glycolytic enzyme deficiency
hemolytic anemia related to decreased ATP and cell membrane alterations
can treat with folic acid if severe
causes of lactic acidosis
- impaired oxidation of pyruvate to acetyl-CoA
- excess NADH production related to ethanol consumption
- strenuous exercise
- severe thiamine def
- pyruvate carboxylase def
MI “paradox”
decreased O2 leads to increased glycolysis
increased glycolysis leads to increased lactate
increased lactate leads to decreased pH
decreased pH inhibits phosphofructokinase = decreased ATP production
