BIOC 503 - Gluconeogenesis

functions of gluconeogenesis

make glucose from non-carbohydrate precursors when blood sugar levels are LOW and not enough glycogen is stored in liver a kidneys

• makes glucose from glycerol, amino acids, and lactate

starved

gluconeogenesis happens under ___ conditions

glycerol kinase, triose phosphate isomerase

from glycerol to glucose:

1- glycerol (from triglycerides metabolism aka fatty acids metabolism) turned into glycerol-3-phosphate by ___

2- glycerol-3-phosphate turned into dihydroxyacetone phosphate via ___

3- reverse glycolysis

alanine aminotransferase, lactate dehydrogenase

Alanine and lactate are both turned into pyruvate to make glucose in gluconeogenesis

• alanine made into pyruvate by ___

• lactate made into pyruvate by ___

pyruvate carboxylase, phosphoenolpyruvate carboxykinase

glucose from amino acids/lactate:

1- made into pyruvate by either lactate dehydrogenase or alanine aminotransferase

2- pyruvate turned into oxaloacetate by ___

3- oxaloacetate turned into phosphoenolpyruvate (PEP) via ___

4- reverse glycolysis

biotin

pyruvate carboxylase turns pyruvate into oxaloacetate in gluconeogenesis

• requires cofactor ___ (vitamin B7)

• requires ATP and CO2

• activated by acetyl-CoA

GTP

phosphoenolpyruvate carboxykinase used in gluconeogenesis to turn oxaloacetate into PEP

• requires ___

• activated gene expression by glucagon

reversible

gluconeogenesis runs the ___ reactions of glycolysis in the opposite way, only requiring other enzymes for the irreversible reactions of glycolytic pathway

fructose-1,6-biphosphatase

gluconeogenesis enzyme turning fructose-1,6-biphosphate back into fructose-6-phosphate

• inhibited by fructose-2,6-biphosphate

• activated by citrate

glucose-6-phosphatase

enzyme of gluconeogenesis allowing glucose-6-phosphate (G6P) to be turned back into glucose

• ONLY PRESENT IN LIVER

• gene expression induced by glucagon

glucokinase

enzyme found in the LIVER that also phosphorylates glucose to make G6P just like hexokinase does in all other tissues

• high a high Km for glucose, so it is only activated at very high glucose concentration

hypoglycemia

glucose-6-phosphatase deficiency causes severe ___ as liver cells unable to make glucose from G6P either from glycogen degradation or gluconeogenesis

glucagon

If a person does not recover normal blood sugar levels after ___ injection, then they have an issue with gluconeogenesis

counter regulatory-mechanisms

gluconeogenesis and glycolysis are subjected to ____

frcutose-2,6-biphosphate

___ activates phosphofructokinase-1 in glycolysis & inhibits fructose-1,6-biphosphatase in gluconeogenesis

phosphofructokinase-2

aka PFK2

• turns fructose-6-phosphate into fructose-2,6-biphosphate

• inhibited by PKA aka inhibited by glucagon and epinephrine aka inhibited by low blood sugar = no more inhibitor of gluconeogenesis

• activated by insulin

frcutose-2,6-biphosphatase

• turns fructose-2,6-biphosphate into fructose-6-phosphate

• activated by PKA = activated by glucagon and epinephrine = less frcutose-2,6-biphosphate = MORE gluconeogenesis

• inhibited by insulin