L-57 Amino Acid Degradation And Urea Cycle

Front 1

Circumstances in which amino acids used for energy

Back 1

1. Normal synthesis/degradation of protein

2. Overly protein-rich diet (amino acids cannot be stored)

3. Starvation or disease, e.g. T1DM

Front 2

Protein digestion in stomach

Back 2

1. Gastric mucosa secrete gastrin

2. Gastrin stimulates secretion of HCl and pepsinogen.

3. pH drops - antiseptic effect and denatures globular proteins

Front 3

Peptide digestion in small intestine

Back 3

1. Low pH triggers secretion of secretin which stimulates pancreas to secrete bicarbonate, neutralizing the pH.

2. Entrance of amino acids triggers release of cholecystokinin which stimulates secretion of zymogen enzymes (pepsinogen, trypsinogen, chymotrypsinogen)

Front 4

Acute Pancreatitis

Back 4

Obstruction of zymogen secretion from gallstones or alcoholism causes zymogens to be activated in and degrade the pancreas.

Front 5

Transamination

Back 5

Amino acid + alpha-KG -aminotransferase PLP-> alpha keto acid + glutamate

Enzyme Lys attacks PLP so PLP transiently carries amine group. Transitions between aldehyde form and aminated form that donates amino group.

Front 6

Pyridoxine-dependent Epilepsy

Back 6

Missing ASD, enzyme that generates PLP from vitamin B6. Treat with Vitamin B6 and restrict lysine.

Front 7

Glutamate-Alanine Cycle

Back 7

Muscle - glutamate is converted to alpha ketoglutarate, passing amino to pyruvate to form alanine.

Alanine travels through lbood to liver, where it is converted back to pyruvate, passing amino to alpha-ketoglutarate to form glutamate.

Pyruvate is passed from liver to muscle via glucose.

Front 8

Unloading of Amino from Glutamate

Back 8

Oxidative deamination - requires O2 to convert amino acid to keto acid.

glutamate -glutamate dehydrogenase-> ketoglutarate + NH4+

Front 9

Glutamine transport

Back 9

Glutamate -glutamine synthetase-> delta glutamyl phosphate

Delta glutamyl phosphate + NH4 -glutamine synthetase-> glutamine

Glutamine travels in blood to liver.

Front 10

Urea Cycle

Back 10

NH4 + HCO3 -carbamoyl phosphate synthetase-> carbamoyl phosphate

Ornithine + Carbamoyl Phosphate -ornithine transcarbamylase-> Citruline

Citruline + Aspartate -arginiosuccinate synthetase-> Arginosuccinate

Arginosuccinate -arginosuccinate lyase-> Fumarate + Arginine

Arginine -arginase-> Urea + Ornithine

Front 11

Ketogenic amino acids

Back 11

Leucine and lysine are exclusively ketogenic.

Front 12

Amino acid degradation - Pyruvate

Back 12

C T S W A G

Cysteine

Threonine

Serine

Tryptophan

Alanine

Glycine

Front 13

Amino acid degradation - Acetyl coA

Back 13

W Y F L K I T

Tryptophan - most complex

Tyrosine

Phenylalanine

Leucine

Lycine

Isoleucine

Threonine

Front 14

Amino acid degradation - alpha ketoglutarate

Back 14

Q H E P R

Glutamine

Histidine

Glutamate

Proline

Arginine

Front 15

Amino acid degradation - oxaloacetate

Back 15

Asparagine

Aspartate

Front 16

Amino acid degradation - succinyl-coA

Back 16

M I T V

methionine

isoleucine

threonine

valine

Front 17

Branched chain amino acids

Back 17

Leucine, isoleucine, and valine are not degraded in the liver - oxidized in muscle, kidney, fat, and brain using branched-chain aminotransferases to generate ketoacids.

Front 18

Cofactors for one-carbon transfers

Back 18

Biotin - transfers CO2 - most oxidized carbon state

Tetrahydrofolate - transfers CH3 - intermediate carbon state

S-adenosylmethionine (adoMet) - transfers CH3 - most reduced carbon state.

Front 19

Glycine encephalopathy

Back 19

Second most common disorder of amino acid catabolism, caused by AR defects in glycine cleavage enzyme (PHTL). Involved in conversion of threonine and glycine to pyruvate.

Elevated glycine levels.

Front 20

PKU

Back 20

Build up of phenylalanine causing intellectual disability and delayed development. Most common disorder of amino acid metabolism.