Interorgan Amino Acid Catabolism

Front 1

What happens to the remaining carbon skeletons following removal of the (alpha)-amino nitrogen.

Back 1

they enter glycolysis or the TCA cycle at seven points

Front 2

What are the three classes of amino acid carbon skeletons?

Back 2

glucogenic, ketogenic, or both glucogenic and ketogenic

Front 3

What do glucogenic amino acids form after they enter the TCA cycle?

Back 3

lead to a net increase in OAA

Front 4

What do ketogenic amino acids form after they enter the TCA cycle?

Back 4

they form acetyl CoA or acetoacetate

Front 5

What are the three branched chain amino acids (BCAAs) and where are they metabolized?

Back 5

leucine, isoleucine, and valine - metabolized in the peripheral tissues (skeletal muscle, brain)

Front 6

What are branched chain amino acids (BCAAs) needed for?

Back 6

protein synthesis, increased leucine increases insulin secretion, increases protein synthesis, and decreases protein degradation, BCAAs are also needed for hair, sythesis of glutamate and glutamine, and for energy

Front 7

What enzymes are used to regulate the catabolism of branched chain amino acids (BCAAs)?

Back 7

BC aminotransferase (brain) generates BC (alpha)-keto acids and funnels nitrogen into glutamate, branched chain (alpha)-keto acid dehydrogenase complex (BCKADHC) is the rate limiting step in BCAA catabolism

Front 8

What are the fates of the three branched chain amino acids after they have been completely catabolized?

Back 8

leucine - ketogenic (acetoacetyl CoA)
valine - glucogenic (succinyl CoA)
isoleucine - keto- and glucogenic (acetyl CoA and succinyl CoA)

Front 9

What are the MI TV amino acids and what are their functions?

Back 9

methionine, isoleucine, threonin, and valine: they are converted to propionyl CoA and on to succinyl CoA during catabolism

Front 10

How does the ammonia generated in the peripheral tissues from the catabolism of BCAAs get to the liver without causing toxicity?

Back 10

the (alpha)-amino groups removed during the catabolism of BCAAs aer used to synthesize alanine and glutamine (non-toxic)

Front 11

What is the purpose of the alanine cycle and which tissues are used in the cycle?

Back 11

allows nitrogen to be transported from muscle to the liver without contributing to hyperammonemia

Front 12

What is the most common inherited amino acid metabolism disease?

Back 12

cystinuria

Front 13

What causes maple syrup urine disease (MSUD) and what are the effects?

Back 13

due to absence or reduced activity of BCKADHC (second, and rate limiting step of BCAA catabolism), causes increased circulating levels of BCAA and their (alpha)-keto acid derivatives (ketoacidosis), also causes hypoalanemia (from inhibition of alanine cycle) and coma (from glutamate, glutamine)

Front 14

What is the treatment of maple syrup urine disease (MSUD)?

Back 14

remove BCAAs from diet

Front 15

What causes Alkaptonuria (homogentisic aciduria) and what are the effects?

Back 15

caused by a defect in homogentisic acid oxidase (degrades phenylalanine and tyrosine), leads to accumulation of homogentisic acid which causes dark urine, osteoarthritis, heart valve problems, kidney stones

Front 16

How is Alkaptonuria treated?

Back 16

low protein diet and vitamin C

Front 17

How does the enzyme activity of nonessential amino acid catabolism differ from that of essential amino acid catabolism?

Back 17

enzyme activity increases in proportion with amino acid increase in non-essential amino acids, enzyme activity is only active after a threshold amino acid level is reached with essential amino acids

Front 18

Which metabolic processes are very active after a high protein, low carbohydrate meal?

Back 18

urea cycle, (beta)-oxidation, and gluconeogenesis

Front 19

Why is amino acid catabolism active in fed and fasting states?

Back 19

fed: substrate availibility
fasting: covalent modification (phosphorylation) of enzymes by glucagon (catabolism of non-essential amino acids)