Glycolysis Flashcards
rate-limiting enzyme in glycolysis
Phosphofructokinase-1
2 things that increae activity of phosphofructokinase-1 (PFK-1)
- AMP
2. fructose 2,6 bisphosphonate
2 things that inhibit PFK-1
- ATP
2. Citrate
beginning enzyme in glcolysis (depending on tissue)
hexokinase or glucokinase
*glucokinase in liver and beta cells of pancreas; hexokinase everywhere else
differences between hexokinase and glucokinase
- glucokinase–> has a low affinity (high Km), is induced by insulin, and a very high Vmax; ensures liver and pancreas B cells only take up glucose when it is plentiful
- hexokinase–> high affinity (low Km), low Vmax, and NOT induced by insulin
catalyzes phosphoenol pyruvate–> pyruvate; last step in glycolysis
Pyruvate kinase
what induces pyruvate kinase activity
- fructose 1,6 bisphosphonate
what two things decrease pyruvate kinase activity
- ATP
2. Alanine
increased glucagon in fasting state does what to decrease glycolysis and increase gluconeogenesis
glucagon–> activates PKA–> phosphorylates fructose bisphosphatase-2/ phosphofructokinase-2 complex–> activates FBP-2 to convert Fructose 2,6 bisphosphate to fructose 6 phosphate = used in gluconeogenesis
increased insulin during fed state does what to decrease gluconeogenesis and increase glycolysis
insulin–> decreases cAMP and thus PKA activity–> unphosphorylated FBP-2/ PFK-2 complex means more active PFK-2–> converts fructose-6-phosphate to fructose 2,6 phosphate, which increaes activity of Phoshofructokinase-1 = increased glycolysis (PFK-1 converts fructose 6 phosphate to fructose 1,6 bisphosphate, remember PFK-1 is rate-limiting enzyme in glycolysis)
what is the clinical consequence of a glycolytic enzyme deficiency?
hemolytic anemia–> RBC only can use glycolysis, so when its gone, cant make ATP, so Na/K pumps fail, cell swells and lyses
MCC of glycolytic enzyme deficiency
pyruvate kinase deficiency
