Biochem-AAs

Question 1

Name the essential amino acids:

Answer 1

PVT TIM HALL
Phenylalanine 
Valine 
Threonine
Tryptophan 
Isoleucine 
Methionine 
Histidine
Arginine*
Leucine
Lysine

Question 2

1. Tyrosine is synthesized from _____.

2. Cysteine is synthesized from _____.

Answer 2

1. Phenylalanine

2. Methionine

Question 3

Most transaminases require what?

Answer 3

Alpha ketoglutarate and glutamate

* they all require pyridoxal phosphate as a prosthetic group

Question 4

Of the 20 AAs which are not substrates for reversible transamination

Answer 4

Lysine

Threonine

Question 5

What AAs are synthesized from alpha ketoglutarate?

Answer 5

Glutamate
Glutamine
Arginine
Proline

Question 6

What AAs are synthesized from oxaloacetate?

Answer 6

Aspartate

Asparagine

Question 7

What AAs are synthesized from 3-phosphoglycerate?

Answer 7

Serine
Glycine
Cysteine

Question 8

What AAs are synthesized from pyruvate?

Answer 8

Alanine

Question 9

Alanine reactions:

Answer 9

Transamination with pyruvate via ALT (Alanine transaminase)

Question 10

Aspartate reactions:

Answer 10

Transamination with oxaloacetate via AST (aspartate transaminase)

Question 11

Asparagine reactions:

Both ways

Answer 11

1. Synthesized from aspartate using glutamine as the -NH2 donor via asparagine synthase
2. Catabolized to aspartate by asparaginase

Question 12

Name the branches chain AAs:

Answer 12

Valine
Leucine
Isoleucine

Question 13

___ is an intramitochndrial enzyme complex analogous to pyruvate DH complex. It has the same cofactor requirements as PDH

Answer 13

Branches chain alpha keto acid DH

Question 14

1. Further metabolism of Valine results in what compounds?
2. Leucine?
3. Isoleucine?

Answer 14

1. Propionyl CoA
2. Acetoacetate + Acetyl CoA
3. Propionyl CoA + Acetyl CoA

Question 15

1. Propionyl CoA carboxylase metabolizes propionyl CoA to ____ and requires ___.
2. Methylmalonyl CoA mutate is the final step, leading to ____, and requires ___.

Answer 15

1. D-methylmalonyl CoA, biotin

2. Succinyl CoA, vitamin B12 derived coenzyme

Question 16

What are the hydroxy AAs?

Answer 16

Serine

Threonine

Question 17

Serine maybe synthesized from ___ by what reactions?

It may be metabolized to this substance by what reactions?

Answer 17

• 3-phospholycerate
• oxidation, transamination, and removal of the phosphate by phosphatase
• transamination, reduction, and phosphorylation by glycerate kinase

Question 18

Serine may be converted to 2 other things:

1. Pyruvate by what?
2. Glycine by what?

Answer 18

1. By serine (threonine) dehydratase

2. By serine hydroxymethyl transferase

Question 19

Serine (threonine) dehydratase produces ____ which is converted by _____ to propionyl CoA. The major route is catalyzed by threonine DH and yields ___

Answer 19

1. Alpha-ketobutyrate
2. Alpha-ketoacid DH
3. Acetyl CoA plus glycine or pyruvate

Question 20

Glycine may be synthesized from what three things (and by what for each)?

Answer 20

1. Serine and THF by serine hydroxymethyl transferase
2. Threonine by threonine DH
3. CO2, NH4+, and methylene THF by glycine synthase or glycine de carboxylase

Question 21

Glycine may be catabolized by what two things?

Answer 21

1. Serine hydroxymethyl transferase to serine

2. Glycine decarboxylase

Question 22

THF (tetrahydrofolate) is derived from ____. It serves to ___

Answer 22

1. Folic acid

2. Transfer one carbon units at various oxidation levels

Question 23

Important uses for THF:

Answer 23

1. Serine, glycine, histidine
2. Resynthesis of methionine from homocysteine
3. Synthesis of purines
4. Formation of the methyl group of thymine

Question 24

In the liver and kidney, ____ removes the amine as ammonium ion used for urea synthesis or excretion.

Answer 24

Glutamate DH

Question 25

Glutamate DH acts on what AAs?

Answer 25

Glutamate (glutamine) Proline Arginine Histidine

Question 26

Glutamate is intimately associated with the ___ cycle via ____. Synthesis and catabolism of arginine and proline proceed through the common intermediate ____.

Answer 26

1. TCA 2. Transamination to alpha-ketoglutarate 3. Glutamate gamma-semialdehyde

Question 27

Catabolism of histidine to glutamate involves the formation of ____

Answer 27

N5 formimino THF

Question 28

Some reactions of glutamine synthesis and breakdown produce ___ which is toxic at elevated levels. Glutamine serves as a non-toxic transport form of ___ in the blood. It is converted to alpha-ketoglutarate by ____ or ____ (enzyme?)

Answer 28

NH4+ Ammonia Transamination or oxidative deamination

Question 29

1. Cysteine may be synthesized from homocysteine plus serine in 2 steps. The enzymes in both steps require ___. 2. What are the two enzymes?

Answer 29

1. Pyridoxal phosphate | 2. Crystathionine synthase and cystathionase

Question 30

Conversion of homocysteine to methionine requires a cofactor derived from ____

Answer 30

Vitamin B12

Question 31

The major route of cysteine catabolism is through ____ by ____. After transamination, nonenzymatic desulfurylation results in ____

Answer 31

1. Oxidation by cysteine dioxygenase | 2. Pyruvate and sulfite

Question 32

Essentially all of the phenylalanine not used for protein synthesis is converted to ____ by ____, which requires what cofactor?

Answer 32

Tyrosine by phenylalanine hydroxylase | -tetrahydrobiopterin

Question 33

Phenylalanine and tyrosine are catabolized to ____ and _____. Which means what?

Answer 33

Fumarate and acetoacetate | They are both glycogenic and ketogenic

Question 34

____ is inducible by high concentrations of tyrosine and by glucocorticoids

Answer 34

TAT (tyrosine aminotransferase)

Question 35

Tryptophan: 1. The first enzyme of the pathway, ____, is inducible by high concentrations of tryptophan and glucocorticoids. 2. What things are formed during catabolism?

Answer 35

1. Tryptophan oxygenase | 2. Alanine, quinolinic acid, acetyl CoA

Question 36

Lysine catabolism to acetoacetyl CoA 1. The initials step involves what? 2. Subsequent reactions include what?

Answer 36

1. Removal of E amino group | 2. Oxidations, decarboxylations, and transamination

Question 37

Which AAs are catabolized to pyruvate?

Answer 37

``` Alanine Glycine Cysteine Serine Threonine Tryptophan ```

Question 38

Which AAs are catabolized to acetyl CoA?

Answer 38

Threonine Leucine Isoleucine

Question 39

Which AAs are catabolized to acetoacetyl CoA?

Answer 39

``` Leucine Lysine Phenylalanine Tyrosine Tryptophan ```

Question 40

Which AAs are catabolized to oxaloacetate?

Answer 40

Asparagine | Aspartate

Question 41

Which AAs are catabolized to fumarate?

Answer 41

Tyrosine Phenylalanine Aspartate

Question 42

Which AAs are catabolized to succinyl CoA?

Answer 42

Isoleucine Methionine Valine Threonine

Question 43

Which AAs are catabolized to alpha-ketoglutarate?

Answer 43

``` Glutamate Glutamine Histidine Proline Arginine ```

Question 44

Classical PKU (phenylketonuria) is due to what?

Answer 44

Deficiency of phenylalanine hydroxylase | *small percentage of people could have normal phenylalanine hydroxylase but are defective in biopterin metabolism

Question 45

Phenylalanine is particularly toxic to the developing ____. Untreated infants may lose ____ in the first year. Ultimately, 96-98% of untreated PKU patients will have what?

Answer 45

1. CNS 2. 50 IQ points 3. An IQ of less than 50

Question 46

Treatment of PKU

Answer 46

Diet low in phenylalanine | *hose with biopterin problems require THB supplements

Question 47

Tyrosinemia Type 2 (aka ____) is caused by a deficiency in _____. What systems are most likely affected? What is the treatment?

Answer 47

1. Oculocutaneous tyrosinemia, Richner-Hanhart syndrome) 2. Eyes, skin, sometimes CNS 3. Diet low in tyrosine and phenylalanine

Question 48

Neonatal tyrosinemia is due to what?

Answer 48

Maturational delay in activity of p-hydroxyphenylpyruvate oxidase * usually benign * tx is dietary

Question 49

Black urine is a sign of ___, which is due to a deficiency in ___

Answer 49

Alcaptonuria | Homogentisate oxidase

Question 50

1. 2. Tyrosinemia Type 1 (aka ___) is due to a deficiency in ___. 3. What things are affected? 4. Symptoms? 5. Tx?

Answer 50

1. Hepatorenal tyrosinemia 2. Fumarylacetoacetate hydrolase 3. Liver, kidney, peripheral nerves 4. Porphyria like symptoms due to succinylacetone accumulation which inhibits gene synthesis 5. NTBC plus diet

Question 51

What is NTBC?

Answer 51

Orfadin Nitisinone 2-(2-nitro-4-trifluoromethylbenzoyl) cyclohexane-1,3-dione *inhibits pHPPA oxidase

Question 52

MSUD (______) is caused by a deficiency in ____.

Answer 52

Maple syrup urine disease | Branch chain alpha-ketoacid DH