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ATSU - DeBoer > QTR 2 Block 3 Biochemistry: Amino Acid Metabolism and Special Products > Flashcards

QTR 2 Block 3 Biochemistry: Amino Acid Metabolism and Special Products Flashcards

1
Q

Name the essential amino acids.

A

Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, MEthionine, Histidine, Arginine, Leucine, Lysine ( PVT TIM HALL)

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2
Q

What is a transamination reaction?

A

Reaction involved in synthesis or degradation of AA involving transfer of amine groups…usually involves alphaketoglutarate and glutamate

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3
Q

Transaminases require what B vitamin derivative as a prosthetic group?

A

Pyridoxal Phosphate ( Vit B6 derivative)

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4
Q

What two AA are NOT substrates for reversible transamination reactions?

A

Lysine and Threonine

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5
Q

Amino acid metabolism is heavily dependent on coenzymes derived from what?

A

Vitmine B6, B 12, Folate, Biotin, and Niacin

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6
Q

What does it mean for an AA to be glycogenic or ketogenic?

A

These are AA whose carbon skeleton can be converted into glucose or ketones with the help of transaminase reactions.

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7
Q

Where do the carbon skeletons of non-essential AA come from in the body?

A

mainly derived from energy metabolism intermediates or certain essential AA

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8
Q

What TCA intermediates can provide carbon skeletons for glycogenic or ketogenic processes?

A

alphaketoglutarate and oxaloacetate

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9
Q

What glycolytic intermediates can provide carbon skeletons for glycogenic or ketogenic processes?

A

3- phosphoglycerate and pyruvate

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10
Q

Which essential amino acids can provide carbon skeletons for non essential amino acids and ketogenic or glycogenic synthesis?

A

tyrosine and cysteine

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11
Q

A transaminase reaction of this AA can produce pyruvate, and is quantitatively the most important glycogenic AA. What other amino acid is transaminated in this way?

A

Alanine Transaminase (ALT) - requires alphaketoglutarate and glutamate. Aspartate also uses this mechanism.

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12
Q

How do alphaketoglutarate and glutamate participate in transamination reactions?

A

alphaketoglutarate picks up an extra amine group from the AA being transaminated/deaminated, and forms glutamate.

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13
Q

Asparagine uses ______ as an NH3 donor in its transamination.

A

Glutamine

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14
Q

Propionyl CoA can be metabolized to __________, with the help of what two coenzymes?

A

Succinyl CoA; Biotin and Vitamin B12

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15
Q

What are the glycogenic/ketogenic properties of the branched chain amino acids leucine, valine, and isoleucine?

A

Valine is Glycogenic, Leucine is Ketogenic, and Isoleucine is both

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16
Q

How can the non-essential AA serine be synthesized in the body?

A

It can be formed from 3-phosphoglycerate (from glycolysis) via oxidation, transamination, and removal of the phosphate by a phosphatase

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17
Q

How is serine converted to pyruvate?

A

via deamination and dehydration by Serine (Threonine) Dehydratase

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18
Q

How is glycine formed from serine?

A

via “one carbon metabolism” by Tetrahydrofolate (THF) and using serine hydroxymethyl transferase

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19
Q

Is serine glycogenic?

A

YUUP.

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20
Q

By what two pathways is threonine catabolized?

A

It basically has three pathways, and is catabolized in a glycogenic manner to propionyl coA and pyruvate, or in a ketogenic manner to acetyl coA.

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21
Q

The major route in threonine catabolism involves what enzyme?

A

Threonine Dehydrogenase

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22
Q

Glycine may be synthesized from what sources?

A

serine and THF, threonine, and Co2 + NH4 + methylene THF

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23
Q

Glycine is catabolized mainly by ______.

A

serine hydroxymethyl transferase to serine, and glycine decarboxylase

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24
Q

Since glycine may be converted to serine it is considered to be _______.

A

Glycogenic

25
Q

Why is Tetrahydrofolate (THF) important in one carbon metabolism?

A

it serves to transfer one carbon units in a number of reactions

26
Q

The net synthesis AND catabolism of glutamine, proline and arginine share what intermediate compound?

A

Glutamate

27
Q

Catabolism of histidine to glutamate will form what biproduct?

A

N5-formimino THF

28
Q

What is the importance of glutamine in maintenance of blood nitrogen levels?

A

it serves as a non-toxic carrier of NH4 produced by other reactions- it then transfers these carrier NH4 groups to other tissues for the formation of purines for example, and also supplies the bulk of excreted ammonia from the kidneys ( due to glutaminase activity)

29
Q

Cysteine can be synthesized from _____ and _____, and depends on the availability of what other AA?

A

homosysteine plus serine…depends on the availability of methionine

30
Q

The major route of cysteine catabolism is through oxidation by _________.

A

Cysteine Dioxygenase….cysteine is considered glycogenic.

31
Q

Essentially all of the phenylalanine carbon skeleton NOT used for protein synthesis is converted to _______ by what enzyme?

A

tyrosine; phenylalanine hydroxylase

32
Q

Why is tyrosine not considered an essential amino acid?

A

it can be formed by the remnants of phenylalanine

33
Q

This enzyme is inducible by high concentrations of tyrosine and glucocorticoid hormones.

A

Tyrosine Aminotransferase (TAT)

34
Q

What are the important products formed by catabolism of tryptophan?

A

Alanine, quinolinic acid, and acetyl coA ( therefore tryptophan is both glycogenic and ketogenic

35
Q

This initial enzyme in the tryptophan catalysis pathway is inducible by high concentrations of tryptophan and by glucocorticoid hormones.

A

Tryptophan Oxygenase

36
Q

Lysine catabolism forms _______.

A

Acetoacetyl Coa (Ketogenic)

37
Q

This AA disorder involving a deficiency in phenylalanine hydroxylase will result in ____.

A

Phenylketonuria (PKU) …phenylpyruvate is excreted in large quantities

38
Q

This disorder can cause a loss of 50 IQ points in the first year of life and is the one of the most prevalent aminoacidopathies.

A

Phenylketonuria

39
Q

What is the treatment for PKU? What implication does this have for female PKU patients of child bearing age?

A

A diet low in PKU, also a supplementation with oral THB for PKU pts with biopterin defect. Female PKU patients not on dietary management have a 90-97% change of bearing mentally retarded offspring, so should be on a Phe restricted diet prior to planned pregnancy

40
Q

This aminoacidopathy results in opacity of the cornea, skin lesions, and variable degrees of mental retardation in some patients.

A

Tyrosinemia Type 2 ( aka Richner-Hanhart Syndrome)

41
Q

This benign aminoacidopathy results secondary to delayed activity in p-hydroxyphenylpyruvate oxidase.

A

Neonatal Tyrosinemia

42
Q

This historically important disorder results in the passing of black urine, secondary to a homogentisate oxidase deficiency.

A

Alcaptonuria

43
Q

This disorder results in liver failure, renal failure, and painful neurologic symptoms. Due to a deficiency of fumarylacetoacetate hydrolase.

A

Tyrosinemia Type I

44
Q

This disorder results in sweet scented urine due to a branched alpha ketoacid dehydrogenase deficiency, also neurological symptoms and shortened life expectancy. More prevalent in mennonite populations.

A

Maple Syrup Urine Disease (MSUD)

45
Q

What special AA products function as coenzymes for other reactions?

A

SAM, NAD, Coenzyme A and Carnitine

46
Q

Where does the Sulfur atom in CoA-SH come from?

A

Cysteine

47
Q

Catecholamines are derived from what AA??

A

tyrosine (requires tetrahydrobiopterin /THB)

48
Q

What AA is used to make acetylcholine?

A

serine…requires three methyl groups from SAM, and an acetyl group from Acetyl CoA

49
Q

What important neurotransmitters are considered AA special products?

A

Catecholamines, dopamine, acetylcholine, GABA, serotonin, melotonin, NO

50
Q

What AA is serotonin (5-HT) formed from?

A

tryptophan

51
Q

Arginine is used to synthesize which neurotransmitter?

A

Nitrous Oxide

52
Q

What are some specialized functions of NO?

A

used by macrophages in the nitrogenous burst, vascular endothelial vasodilatory factor, CNS second messenger

53
Q

Glycine and arginine are used to synthesize_____.

A

Creatine (also creatinine)

54
Q

What is the function of Glutathione? (aka GSH)

A

it acts as a non-toxic reservoir of reducing power ( instead of using strictly cysteine, which would be toxic)

55
Q

What are the major polyamines, and what is their general function?

A

Putrescine, spermidine, and spermine… used for DNA synthesis ….derived from methionine and ornithine

56
Q

What compounds are needed to form polyamines?

A

Ornithine and SAM

57
Q

What AA is a precursor to melanin?

A

Tyrosine - def. in the enzyme for this conversion results in classical albinism

58
Q

This vasodilator substance is the result of decarboxylation of histidine.

A

Histamine

59
Q

Decarboxylation of serine can form these special products.

A

Choline and Ethanolamine

ATSU - DeBoer (43 decks)

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