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Regulation of Calvin cycle
Rubisco is a prime target for regulation
Activation of rubisco by carbamate
Rubisco is activated by carbamylation
CO2 concentration?
pH?
Alkaline pH favors
Mg2+ concentration?
conditions regulate stromal FBP-1
high light
Stroma pH
And Mg2+
Activation of Rubisco
fig20-34
Redox regulation of Calvin cycle with
Thioredox: Activation of enzymes by
regulating redox states of a disulfide
bond
redox regulation of Calvin cycle enzymes via thioredoxin
high light
fig20-36
Th-SH
enz
activity
Coordination of the light and dark reactions
Light reactions
Electron transfer
Reduced ferrodoxin
Thioredoxin
Regulatory disulfide bonds in Calvin cycle enzymes
Dark reactions
Coordination of the light and dark reactions
Light reactions
Electron transfer
Reduced ferrodoxin
pH
Mg2+
Thioredoxin
Regulatory disulfide bonds in Calvin cycle enzymes
Dark reactions
Fat Metabolism
Americans are getting
fatter, so do the people in
other developed countries
Triacylglycerol:
Fatty acids and
glycerol
Also called triglycerides
or neutral fats
Fatty acids
Various lipids
Dietary fats form micelles with the
help of Bile salts
Lipases release fatty acids and monoacylglycerol
Transport lipids in Chylomicrons
from McDonalds to Metabolism…
Summary of dietary lipids processing
Molecular structure of
Chylomicrons
Mobilization of the stored Triacylglycerol in adipose tissue
Transport fatty acids from adipose tissue to muscle
or other tissue
Serum albumin
Fatty acids and
glycerol are the
products from
lipase cleavage
Fate of glycerol
Physiological roles for fatty acids
Building blocks for phosphalipis and glycolipids
Covalent modification of proteins
Fuel
Precursor for hormones and signaling molecules
Fatty acids are oxidized in matrix of
mitochondria
Activation and transport fatty acids to
mitochondria
Three enzymatic reactions:
Acyl CoA synthetase
Carnitine acyl transferase I
Carnitine acyl transferase II
Activates fatty acid to form Acyl CoA
Driving by hydrolysis of pyrophosphate
Transport Fatty acids into mitochondria
Carnitine
acyltransferase I
Carnitine
acyltransferase II
Formation of Acyl carnitine
Normally, the transfer of an acyl group from an alcohol
to sulfhyfryl group is thermodynamically unfavorable
Four basic steps in b-oxidation
Recurring metabolic motifs
Acyl-CoA dehydrogenase: an enzyme similar to
succinate dehydrogenase
The enzyme is located
on the inner membrane
The product is always
trans
Complex II succinate dehydrogenase
Electron-transferring flavoprotein
fig19-8
Enoyl-CoA hydratase: similar to fumarase
Always L configuration
B-hydroxyl-CoA dehydrogenase: similar to malate
dehydrogenase
Only use L type of substrate
Thiolase
b-oxidation challenges
monounsaturated FA
polyunsaturated FA
odd-carbon FA
An isomerase is
needed for
unsaturated
b-oxidation of
polyunsaturated
fatty acids
fig17-10
b-oxidation of
polyunsaturated
fatty acids
fig17-10
A reductase and an isomerase
Odd-chain fatty acids yield propionyl CoA
Propionyl CoA
carboxylase: biotin
Mutase
the coenzyme B12 reaction
box17-2
Ketosis and ketone bodies
Synthesis of
ketone bodies
Ketone bodies can be regarded as a watersoluble, transportable form of acetyl units,
provide alternative fuels
Ketone bodies are produced in liver and are a major
source of energy for some tissues
From ketone
bodies to acetyl
CoA
Unselfish liver
Diabetes and starvation leads to ketosis