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Biochemistry 2 > Amino acid catabolism > Flashcards

Amino acid catabolism Flashcards

1
Q

What is the trend with protein intake

A

Amount of protein we intake is increasing

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2
Q

Most AA are metabolized in

A

The liver

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3
Q

Amino acids can be metabolized through

A

Amino group and urea cycle

And citric acid cycle

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4
Q

What happens with ammonia and carbon skeleton in principle

A

Ammonia- recycled or excreted

Carbon skeleton- TCA cycle or Glucoenogenesis or ketogenesis

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5
Q

In what parts of GI protein is digested

A

Stomach and small intestine

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6
Q

What enzymes degrade protein

A

Peptin
HCl to unwind
Trypsin
Chemotrypsin

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7
Q

What is the first reaction of amino acids catabolism

A

Removal of an amino group

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8
Q

Describe how removal of the amino group happens

A

Through amino transferase alpha-ketoglutarate is transformed to L-glutamate

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9
Q

What is the effect on amino acids during transamination reaction

A

No net loss, it is just transferred from one molecule to another

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10
Q

Aminotransferases are ___

A

AA specific ( e.g. alanine amino transferase)

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11
Q

What is the cofactor for amino-transferases

A

Pyridoxal phosphate (vit.6)

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12
Q

Vitamin 6 is also a cofactor for

A

Glycogen phosphorylase

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13
Q

What is the function of L-glutamate

A

The glutamate then functions as an
amino group donor for biosynthetic pathways or for excretion pathways that lead to the elimination of
nitrogenous waste products.

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14
Q

Deanimation of glutamate happens in

A

Mitochondria

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15
Q

What enzyme, product and substrates are needed for deanimation reaction in liver

A

Glumate-> alpha-ketoglutarate

Enzyme: glutamate dehydrogenase

Using: NAD(P)+, H2O

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16
Q

The use of alpha-ketoglutarate

A

Used for transamination, TCA cycle or glucoeneogenesis

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17
Q

Most tissues send their amino group in the form of___

A

Glutamine

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18
Q

Explain transport of ammonia from other tissues

A

L-glutamate with glutamine synthase is converted to gamma-Glutamyl phosphate ( in all tissues)

with glutamine synthetase gamma-Glutamyl phosphate is converted to L-glutamine

L-glutamine is transported to the liver

Glitaminase in liver mitochodria converts L-glutamine to L-glutamate

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19
Q

All deanimmation reaction happen in

A

The liver

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20
Q

What muscles have an addition to glutamate transport system

A

Muscles send amino groups also through alanine

When alanine gets to the liver it is converted back to pyruvate in the liver, and then pyruvate can go through glucoenogenesis and glutamate-> urea cycle

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21
Q

how muscles get alanine

A

By converting pyruvate to alanine with alanine aminotransferase

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22
Q

Excretion of amino group happens through

A

Urea cycle

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23
Q

Where does urea cycle begin and where it continues

A

Starts in mitochondria and continues in the cytoplasm

24
Q

What are possible sources for urea to urea cycle

A

Ammonia from intestine (bacterial digestion and amino acid metabolism)

Glutamine

Glutamate ( also from alanine)

25
Q

What happens in before urea cycle in mitochondria

A

Ammonia group (NH4+) is carboxylated and phosphated with carbamoyl phosphate synthetase I

26
Q

How many energy is required for the synthesis of carbomoyl phosphate

A

requires 2 ATPs ( one for enzymatic reaction) and one for addition of a phosphate group

27
Q

what happens in parallel to glutamate converting to alpha-ketoglutarate and donating its NH4+ group

A

Liver cells have TCA cycle itself. So they produce oxaloacetate that is converted to aspartate with aspertate aminotransferase

Happens in mitochondria

28
Q

What happens to carbomyl phosphate

A

It combines with ornithine to yield citrulline with the help of ornitine trans-carbamoylase

29
Q

what happen to citrulline

A

It goes out of the mitochondria, where arginosuccinate synthetase through an intermediate converts to arginosuccinate

30
Q

What two things are required for the step of conversion citrulline to arginosuccinate

A

ATP

And aspartate

31
Q

What happens to arginosuccinate

A

It is broken down into fumarate ( can be used in TCA) and arginine with arginosuccinase

32
Q

What happens to arginine

A

Using arginase, ornithine is synthesized producing urea

33
Q

Urea has how many amino groups and from what sources

A

2 amino groups

1 from glutamate ->citrulline (from various tissues)
1 from aspartate (TCA cycle in the liver)

34
Q

How urea cycle is regulated

A

When acetyl-CoA and glutamate are high - synthesize of N-acetylglutamate

N-acetylglutamate has positive effect on carbomyl phosphate synthetase I

35
Q

Expression of urea cycle enzymes increases during

A

High protein diet ( some AA yield acetyl-CoA in the result of metabolism)

Starvation,tumor, uncontrolled diabetes (body starts to metabolize muscles and protein in the body)

36
Q

Urea cycle cannot continue without

A

The TCA cycle running,because of aspartate, coming from oxaloacetate

37
Q

How fumarate is brought to TCA cycle in mitochodria from cytoplasm

A

Fumurate is converted to malate with fumarase , malate comes in mitochondria and it can be integrated in TCA cycle

38
Q

With what enzyme malate can be converted to oxaloacetate

A

Malate dehydrogenase

39
Q

Where fumurase and malate dehydrogenase are found

A

Both in cytoplasm and in mitochondria

40
Q

Amino acids yielding acetyl-CoA are

A

ketogenic

41
Q

amino acids yielding other end products are

A

Glucogenic

42
Q

After amino group is removed what happens

A

Carbon backbone serves as an intermediate for TCA cycle

43
Q

Amino acids that are both glucogenic and ketogenic

A 
Isoleucine
Pnenylalanine
Threonine
Tryptophan
Tyrosine
44
Q

What amino acids are only ketogenic ( do not yield glucose)

A

Lysine and leucine

45
Q

Pyruvate can be obtained from what AAs

A 
From 
alanine
Tryptophan
Cysteine
Serine
Glycine
Threonine
46
Q

Acetyl-CoA can be obtained from what AAs

A 
Tryptophan 
Lysine
Phenylalanine
Tyrosine
Leucine
Isoleucine
Threonine
47
Q

alpha-ketogluterate can be obtained from what AAs

A 
Proline
Glutamate
Glutamine
Arginine
Histidine
48
Q

Succinyl-CoA can be obtained from what amino acids

A

Methionine
Isoleucine
Threonine
Valine

49
Q

Oxaloacetate can be obtained from what amino acids

A

Asparagine

Aspartate

50
Q

Fumurate can be obtained from what amino acids

A

Phenyalanine

Tyrosine

51
Q

What makes Leucine, Isoleucine and Valine a group

A

They are used as fuel in muscle/adipose tissue/brain

They are called Branched chain amino acids

52
Q

Branched chain aminotransferase is only expressed in

A

Extra-hepatic cells ( outisde liver)

53
Q

How glutamate dehydrogenase is regulated

A

Increased by ADP and decreased by GTP

54
Q

How urea cycle is regulated

A

All four enzymes of urea cycle and carbomoyl phosphate synthase I are regulated by nutritional status (diet and starvation)

55
Q

High energy demand of urea cycle is offset

A

by NADH (2.5 ATP) when malate is cinverted back to oxaloacetate

Biochemistry 2 (17 decks)

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