glycolysis flash Flashcards
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Glycolysis 1st regulated step
Hexokinase (inhibited by G6P)(low Km for glucose)/ Glucokinase (liver and pancreas)(under low BGL, GK in sequestered in nucleus). Trap glucose as G6P in cell
Glycolysis 2nd regulated step
Phosphofructokinase-1. Major regulated step, sugar commited to glycolytic pathway. Inhibitors: ATP and citrate. Activators: F2,6 BP (links glycolysis to hormonal regulation) and AMP
Glyceraldehyde-3P DH
Enzyme requires sulfhydral group from Cys. Generates NADH
Glycolysis 3rd regulated step
Pyruvate kinase. PEP–>Pyruvate + ATP. 3 forms of PK (L: liver, M1/M2: muscle/other, R: RBC)
Cardiac PFK-2
Phosphorylated by insulin-stimulated PKB or AMP-activated PK, when phosphorylated its kinase activity is active (opposite of lver PFK2). Allows heart glycolysis to be active under low energy conditions or when glucose is high (insulin release)
Liver Pyruvate kinase
Activate: High PEP or F 1,6 BP. Inhibit: high ATP, alanine, covalent modification by cAMP dep. PKA (phosphorylation)
PKA
c-AMP dependent Protein Kinase A. Glucagon/ epinephrine activates adenyl cyclase ATP–> c-AMP. Then PKA R2C2 + c-AMP–> R-cAMP + C. Then “C” causes phosphorylation and inactivation of PFK-2 and PK in liver. Liver then exports glucose and makes gluco via gluconeogenesis.
Cori Cycle
Muscle forms lactate to regenerate NAD+ to continue glycolysis. Carbons form lactate reach liver and help make glucose which is exported via blood to muscle.
Fructokinase
Very active in converting Fructose to F1P. Require ATP. IV fructose load causes rapid P depletion
Amylose
Major form of carbohydrate, comes from starch. Repeating glu alpha(1,4) glu
Amylopectin
Starch also. Alpha (1,4) and alpha (1,6)
Lactose
gal beta (1,4) glu
Sucrose
glu alpha (1,2) fru
Endoglycosidase
cleaves alpha (1,4). From salivary amylase. Creates dextrins
cellulose
glu beta (1,4) glu. No human enzymes to hydrolyze
Pyruvate carboxylase
Enzyme to reverse glycolysis. Pyruvate + ATP + CO2 + Biotin –> OAA. Mitochondria. Activated by acetyl-CoA
PEP Carboxykinase
Enzyme to reverse glycolysis. OAA + GTP –> CO2 + GDP + PEP. Cyto.
Fructose 1,6 Bisphosphatase
Enzyme to reverse glycolysis. F1,6BP –> F6P + P. Cyto. Activate: ATP/ citrate. Inhibit: F2,6 BP/ AMP (reverse of PFK1)
G6 Phosphatase
Enzyme to reverse glycolysis. G6P–> Glucose + P. Only in liver and kidney. Cyto.
Pyruvate DH
Inhibited by acetyl-CoA
