Regulation of Calvin cycle

Rubisco is a prime target for regulation

Activation of rubisco by carbamate

Rubisco is activated by carbamylation

CO2 concentration?

pH?

Mg2+ concentration?

Alkaline pH favors

fig20-34

high light

Stroma pHAnd Mg2+

conditions regulate stromal FBP-1

Activation of Rubisco

Redox regulation of Calvin cycle with Thioredox: Activation of enzymes by regulating redox states of a disulfide bond

fig20-36

high light Th-SHenz

activity

redox regulation of Calvin cycle enzymes via thioredoxin

Coordination of the light and dark reactions

Electron transfer

Reduced ferrodoxin

Thioredoxin

Regulatory disulfide bonds in Calvin cycle enzymes

Light reactions

Dark reactions

Coordination of the light and dark reactions

Electron transfer

Reduced ferrodoxin

Thioredoxin

Regulatory disulfide bonds in Calvin cycle enzymes

Light reactions

Dark reactions

pHMg2+

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 -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

fig19-8

Complex II succinate dehydrogenase

Electron-transferring flavoprotein

Enoyl-CoA hydratase: similar to fumarase

Always L configuration

B-hydroxyl-CoA dehydrogenase: similar to malate dehydrogenase

Only use L type of substrate

Thiolase

-oxidation challenges

monounsaturated FA

polyunsaturated FA

odd-carbon FA

An isomerase is needed for unsaturated

-oxidation ofpolyunsaturatedfatty acids

fig17-10

-oxidation ofpolyunsaturatedfatty 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 water-soluble, 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