Lecture 20 - Amino Acid Catabolism

Question 1

_________ reactions remove amino groups from amino acids via production of free ammonia.

Answer 1

deamination

Question 2

_______ reactions remove amino groups from AA via reversible transfer of an amino group to a common acceptor (keto group) - usually a-ketoglutarate.

Answer 2

transamination

Question 3

AA are classified as glucogenic or ketogenic based on what property?

Answer 3

what the carbon skeleton is converted to (makes glucose vs. makes FAs)

Question 4

Ketogenic AA are degraded to _______ or _______.

Answer 4

acetyl-CoA or acetoacetyl-CoA

Question 5

In general, which two types of AA are important ketogenic AAs?

Answer 5

1. Branched chain AA

2. Aromatic AA

Question 6

What are two major reactions that prevent accumulation of ammonia from amino acid metabolism in peripheral tissues?

Answer 6

1. Alanine transaminase reaction (ALT)

2. Aspartate transaminase reaction (AST)

Question 7

What are the three principal a-keto acids that serve as acceptors of amino groups?

Answer 7

1. a-ketoglutarate
2. Oxaloacetate
3. Pyruvate

Question 8

__________ is an a-keto acid that acts as a nitrogen acceptor in most transaminase reactions and accepts amino groups from glutamate.

Answer 8

a-ketoglutarate

Question 9

________ acts as an acceptor for some amino groups from glutamate in the liver. It accepts amino groups from aspartate.

Answer 9

Oxaloacetate

Question 10

________ is a major acceptor of nitrogen in skeletal muscle (ALT). It accepts amino groups from alanine.

Answer 10

Pyruvate

Question 11

________ is also known as glutamate:pyruvate transaminase and acts in skeletal muscle to produce alanine.

Answer 11

ALT

Question 12

________ is also known as glutamate:oxaloacetate transaminase and forms aspartate.

Answer 12

AST

Question 13

Vitamin B6 is a precursor for ________, which is a coenzyme in transamination reactions and some deamination reactions.

Answer 13

pyridoxyl phosphate

Question 14

Describe the 4 steps involved in the incorporation of the AA nitrogen (in muscle) to glutamate/asparate in liver.

Answer 14

1. N transferred to alanine
2. Alanine transported to liver
3. N transferred from alanine to glutamate (ALT)
4. N transferred from glutamate to aspartate (AST)

Question 15

_______ reacts with pyridoxal to prevent it from being phosphorylated by pyroxidal kinase.

Answer 15

Isoniazid - drug used in treatment of TB

Question 16

_____ inactivates pyridoxal and is used to treat Wilson’s disease (Cu2+ storage disease).

Answer 16

Penicillamine

Question 17

In MI, serum levels of ______ are increased.

Answer 17

AST

Question 18

In muscular dystrophy, serum levels of ______ are increased.

Answer 18

ALT

Question 19

What are 3 conditions in which serum levels of transaminases are decreased?

Answer 19

1. Nutritional pyridoxine deficiency
2. Pregnancy
3. Hemodialysis

Question 20

In order for transaminase to be returned to normal activity levels after treatment with isoniazid or penicillamine therapy, excess _______ is required.

Answer 20

pyridoxine - vitamin B6