BHS 150.2 – Biochemistry II
Notetaker: Elisabeth Anderson






Date: 1/28/2013, 1st hour
Page1
Gluconeogenesis
o Take non carbohydrate sources for carbons and use them to make glucose
o Most frequently used non carbohydrate source is lactate
 Lactate is made using lactate dehydrogenase
 Lactate travels back to liver and is used to make glucose
o Amino acids are also used to make glucose
 Mainly alanine but can also use glutamine
 Lactate is highest
o Lactate and alanine can be converted to pyruvate
o Glycerol is also used to make glucose
o Can get amino acids from Kreb’s cycle
 Intermediate is OAA
 OAA can be used to make glucose
o Gluconeogenesis is basically the reverse of glycolysis
 Can take the end products of glycolysis and use them for gluconeogenesis
 Have to bypass 3 important steps of glycolysis
o Occurs predominantly in the liver cells
 Also present in kidney and maybe intestine cells
 Kidney is back up plan for gluconeogenesis
Enzymes of gluconeogenesis
o 3 key enzymes from glycolysis that need to be bypassed in gluconeogenesis
 Need to be reversed because they use ATP
 Reversed with phosphatases that take off phosphates
 1. Glucokinase
o Enzyme that traps glucose in the cell
 2. Phosphofructokinase-1
o Adds phosphate group to fructose-6-phosphate
 3. Pyruvate kinase
o Making ATP
Pathways are highly regulated
o Do not want to be running both pathways at the same time because that would be wasting lots of
energy
Pathway
o Start with alanine, lactate, and other amino acids from pyruvate
o First step is to get pyruvate back to PEP
 Use two enzymes
 Pyruvate carboxylase
o Converts pyruvate to OAA
o Occurs in mitochondria
o OAA needs to be moved out of the mitochondria into the cytosol
 In the cytosol is PEP carboxykinase
o Uses GTP and converts the OAA to PEP
 This process has to happen twice to get six carbons
o Next steps are the same as glycolysis just in reverse
 Focus on the new enzyme names
 These will be tested
 Goal is to rearrange the electrons in the carbons and phosphate groups to combine
together to get fructose-1,6 biphosphate
o Next need to convert fructose 1,6 biphosphate to fructose 1,6 phosphate bypassing PFK1
 The enzyme fructose 1,6 biphosphotase removes the phosphate
 Conversion using mutase to get glucose 1,6 phosphate from fructose 1,6 phosphate
 Glucose 6 phosphotase removes phosphate group to end up with glucose
Energy
o Takes 6 ATPs to make glucose
Regulation
BHS 150.2 – Biochemistry II
Notetaker: Elisabeth Anderson
o
Date: 1/28/2013, 1st hour
Page2
Cori cycle - Compartmentalization
 Lactate is most commonly made in the muscle
 Excellent at working under low oxygen conditions
o Produces lactate or lactic acid
o This then moves out into the blood and travels to the liver
o The liver uses the lactate for gluconeogenesis
 Glycolysis occurs in the muscle and gluconeogenesis occurs in the liver
 Occurring in different places so it is easily regulated
 Two times when gluconeogenesis is highest
 During exercise involving the muscles or weight lifting puts the body under
stress and produces lactic acid stimulating gluconeogenesis
 Under dietary restrictions when you aren’t taking in glucose
 Regulated by pathway itself
 Two key regulation points
o Fructose 2,6 biphosphate
 Regulatory compound
 Indication of what is needed
 Do I need glycolysis to speed up or gluconeogenesis
to speed up?
 When there is a lot of fructose 2,6 biphosphate available this
means that there is a back-up of fructose 6 phosphate
 Normally fructose 6 phosphate is converted to fructose 1,6
biphosphate by the enzyme PFK1
 When there is a lot of fructose 6 phosphate another enzyme
PFK2 will be activated to convert fructose 6 phosphate to
fructose 2,6 biphosphate
 PFK2 is regulated by phosphorylation levels
 When phosphorylated it is inactive
 When dephosphorylated it is active
 Fructose 2,6 biphosphotase will reverse the process and break
down fructose 2,6 biphosphate to fructose 6 phosphate
 This fructose 6 phosphate can be used in either glycolysis or
gluconeogenesis wherever it is needed
 Scenario
 Glycolysis is happening a lot
 Fructose 6 phosphate is normally converted to fructose 1,6 biphosphate by PFK1
 There is a backup of fructose 6 phosphate
 This means there is more fructose 6 phosphate than fructose 1,6 biphosphate
 This excess causes PFK2 to become activated
 PFK2 causes fructose 6 phosphate to be converted to fructose 2,6 biphosphate
 Fructose 2,6 biphosphate will stimulate PFK1
 Fructose 2,6 biphosphate says to PFK1 “lets speed glycolysis up”
 Need to be able to use all the glucose that is coming in so it needs to work faster
 Once fructose 6 phosphate levels start to decline because glycolysis becomes
more efficient PFK2 will no longer be active but fructose 2,6 biphosphotase will
be active
 Fructose 2,6 biphosphate cannot be used for anything so it must be broken down
by fructose 2,6 biphosphotase back into fructose 6 phosphate so it can go
through the rest of glycolysis
 This removes the stimulus on PFK1 which is a signal to the cell that glycolysis
can be slowed back down
 To keep the process moving forward so that the fructose 1,6 biphosphate that
was just made is not immediately converted back to fructose 6 phosphate
fructose 1,6 biphosphotase is inhibited by fructose 2,6 biphosphate
BHS 150.2 – Biochemistry II
Notetaker: Elisabeth Anderson
Date: 1/28/2013, 1st hour
Page3





This inhibits gluconeogenesis and moves the process forward
Fructose 2,6 biphosphate is the key for regulation
1- part of glycolysis or gluconeogenesis (PFK1, fructose 1,6 biphosphate,
fructose 1,6 biphosphotase)
 2- part of regulation and never fed into glycolysis (PFK2, fructose 2,6
biphosphate, fructose 2,6 biphosphotase)
o Regulated by pyruvate kinase
 Pyruvate kinase is regulated by insulin and glucagon
 When insulin is around pyruvate kinase is active
o Lots of glucose coming in so want to be able to use it by putting it
through glycolysis
 Insulin dephosphorylates pyruvate kinase and makes it active
 Glucagon will add a phosphate group and make it inactive
o When glucose levels are lower
o So we want to inactivate pyruvate kinase to allow pyruvate
carboxykinase and PEP carboxykinase to be active so gluconeogenesis
will occur
o Want gluconeogenesis to be occurring, not glycolysis so more glucose
can be made
o PEP carboxykinase will feed up through gluconeogenesis
 Insulin and glucagon regulate PFK2 and fructose 2,6 biphosphotase through the
same type of mechanism that pyruvate kinase is regulated
o Whenever it is dephosphorylated it is active
o When it is phosphorylated it is inactive
Ketone bodies
o Other metabolic fuel that the cell can be used
o Used under conditions of fasting or starvation
o Become relevant when we have moved away from the supply of glucose
What can happen to glucose?
o It gets converted to glucose 6 phosphate
o Then it goes into glycolysis or it can be used to make glycogen
o It is regulated by glucagon and insulin
o If the glucose 6 phosphate goes through glycolysis you can get:

energy from the Kreb’s cycle

Acetyl CoA for fatty acid synthesis
 Can go through pentose phosphate pathway to make NADPH
 Acetyl CoA for Kreb’s cycle
o How does the cell determine what to do with all the stuff?
 How is the process regulated?
 Hormonal regulators
o Insulin is around when there is an abundance of glucose
o Glucose is around when there are low amounts of glucose
 Always a balance of the two hormones
 Insulin stimulates
 Fatty acid synthesis
 Glycogenesis: the building of glycogen
 Glycolysis
 Lipogenesis: building of lipids
 Protein synthesis
 Glucagon stimulates
 Fatty acid oxidation to release the acetyl coA to make energy
 Gluconeogenesis
 Glycogenolysis: the breakdown of glycogen
 Lipolysis: breakdown of lipids
BHS 150.2 – Biochemistry II
Notetaker: Elisabeth Anderson
Date: 1/28/2013, 1st hour
Page4

Proteolysis