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BIOCHEMISTRY LEC > LESSON 2: AMINO ACIDS AND PEPTIDES > Flashcards

LESSON 2: AMINO ACIDS AND PEPTIDES Flashcards

1
Q

First newborn screening test introduced

A

(early 1960s)

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2
Q

PKU

A

Phenylketonuria

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3
Q

Phenylketonuria enzyme deficient

A

Phenylalanine hydroxylase

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4
Q

Phenylalanine is converted to ________ by PAH

A

Tyrosine

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5
Q

phenylalanine metabolites

A

phenylpyruvic acid,
phenylpyruvate (also known as phenylketone),
and phenyllactic acid

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6
Q

Chronically high levels of phenylalanine and some of its metabolites→

A

brain problems

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7
Q

Hyperphenylalaninemia cases that are not the
result of the lack of the PAH enzyme

A

Deficiency in the enzymes for regeneration and
synthesis of tetrahydrobiopterin (BH4)

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8
Q

cofactor for enzymatic hydroxylation of the
aromatic amino acids

A

BH4

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9
Q

aromatic amino acids

A

phenylalanine,
tyrosine,
tryptophan

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10
Q

Phenylalanine levels

A

> 1,200 μmol/L
Newborn: = 120 μmol/L (2 mg/dL)

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11
Q

Phenylketonuria Metabolites Clinical Presentation

A

blood and urine (characteristic musty odor)

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12
Q

Women with PKU (untreated during pregnancy):

A

microcephalic and mentally retarded babies

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13
Q

Phenylketonuria Clinical Presentation

A

Mental retardation,
failure to walk or talk,
failure of growth,
seizures and tremor
Defect in myelin formation

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14
Q

__________ in brain impairs the transport and metabolism of other aromatic amino acids (tryptophan and tyrosine)

A

phenylalanine

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15
Q

Tryptophan synthesis →

A

serotonin

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16
Q

__________ is the pigment synthesized from tyrosine by tyrosinase:

A

Melanin

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17
Q

light skin colour, fair hair, blue eyes

A

pigmentation hypopigmentation

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18
Q

Phenylketonuria Management

A

Sapropterin dihydrochloride (Kuvan®)
Pegvaliase-PQPZ (Palynziq®)
Dietary Management

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19
Q

Reduce phenylalanine levels by increasing the activity of the PAH enzyme

December 2007, the U.S. Food and Drug Administration (FDA): first drug to help manage PKU

A

Sapropterin dihydrochloride (Kuvan®)

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20
Q

Proven to reduce blood Phe levels in adults with PKU: uncontrolled blood Phe levels on existing management

First FDA-approved enzyme substitution therapy as of 2018, substitutes a PEGylated version of the enzyme phenylalanine ammonia lyase for the deficient PAH enzyme

A

Pegvaliase-PQPZ (Palynziq®)

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21
Q

PEGylated

A

Polyethylene glycol

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22
Q

PEGylated MOA

A

Stealth against the immune system

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23
Q

Breakdown of Aspartame

A

Aspartate
Phenylalanine
Methanol

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24
Q

Phenylketonuria Dietary Management

A

Dietary restriction of phenylalanine with tyrosine supplementation (since phenylalanine is the precursor of tyrosine)

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25
Q

Characterized by the excretion of
tyrosine and tyrosine catabolites in
urine

A

Tyrosinemia

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26
Q

Low levels of the enzyme fumarylacetoacetate hydrolase: last in the series of five

A

Type I Tyrosinemia

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27
Q

Type I Tyrosinemia Clinical Presentation

A

Failure to thrive,
diarrhea
vomiting,
jaundice,
cabbage-like odor,
distended abdomen,
swelling of legs,
increased predisposition for bleeding.

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28
Q

Type I Tyrosinemia Organs affected

A

Leads to liver and kidney failure,
problems affecting the nervous system,
an increased risk of cirrhosis or liver cancer

29
Q

Type I Tyrosinemia Management

A

Nitisinone (also known as NTBC)
Diet

30
Q

Potent reversible inhibitor of 4-hydoxyphenlypyruvate
deoxygenase

A

Nitisinone (also known as NTBC)

31
Q

Type I Tyrosinemia Diet

A

prescribed a low-phenylalanine, low tyrosine diet

32
Q

AKA Richner-Hanhart syndrome

deficiency of the enzyme tyrosine aminotransferase: first in the series

A

Type II Tyrosinemia

33
Q

Type II Tyrosinemia Clinical Presentation

A

Mentally retarded
Excessive tearing,
photophobia (abnormal sensitivity to light),
eye pain and redness,
painful skin
lesions on the palms and soles of the feet.

34
Q

Type II Tyrosinemia Symptomatic Management

A

Limit certain amino acids, such as phenylalanine and tyrosine

Dietary restriction of tyrosine, phenylalanine and methionine (avoid milk and dairy products, meat, fish chicken, eggs, beans and nuts is recommended)

Keratolytics and emollients for hyperkeratotic skin lesions

Oral retinoids for persistent keratoderma.

35
Q

Rare disorder (only a few cases have been reported)

Deficiency of the enzyme 4- hydroxyphenylpyruvate dioxygenase: second of the series of five

A

Type III Tyrosinemia

36
Q

Type III Tyrosinemia Clinical Presentation

A

Mild mental retardation,
seizures, and
periodic loss of balance and coordination

37
Q

Type III Tyrosinemia Management

A

Follow a phenylalanine- and tyrosine-restricted diet

38
Q

Defective enzyme: homogentisate oxidase in tyrosine metabolism

A

Alkaptonuria

39
Q

➢Homogentisate (on standing):

A

oxidized by polyphenol oxidase → benzoquinone acetate → polymerization → pigment called alkapton (black or brown)

40
Q

urine of alkaptonuric patients resembles _________ in color

A

coke

41
Q

Alkaptonuria Clinical Presentation

A

Ochronosis
Arthritis
Signs of aortic or mitral valvulitis

42
Q

Alkaptonuria Management

A

➢Ascorbic Acid
➢ Nitisinone

43
Q

Absence or greatly reduced activity of the enzyme branched-chain α-ketoacid dehydrogenase → blocking normal metabolism of leucine, isoleucine, and valine

A

Maple Syrup Urine Disease (MSUD)

44
Q

Valine →

A

propionyl CoA

45
Q

Isoleucine →

A

propionyl CoA and acetyl CoA

46
Q

Leucine →

A

acetoacetate and acetyl CoA

47
Q

Maple Syrup Urine Disease (MSUD) Clinical Presentation

A

Characteristic maple syrup or burnt sugar odor

Accumulation of the branched chain amino acids and corresponding ketoacids

Neurological complications in babies

48
Q

Pathophysiology valine

A

alpha-ketoisovalerate

49
Q

Pathophysiology isoleucine

A

alpha -keto-β-methylvalerate

50
Q

Pathophysiology leucine

A

alpha-ketoisocaproate

51
Q

Maple Syrup Urine Disease (MSUD) Management

A

Thiamine -> Essential coenzyme in carbohydrate and amino acid metabolism.

Dietary restriction of branched-chain AA

52
Q

Defective transport of cystine and basic amino acids across renal tubule and the small intestine.

Autosomal-recessive defect involving the gene that codes for cystine transporter known as SLC3A1 (SLC for solute carrier)

A

Cystinuria

53
Q

Cystinuria amino acids:

A

cystine
ornithine,
lysine, and
arginine

54
Q

Cystinuria Clinical Presentation

A

Formation of cystine stones in the kidney,
Chronic urinary tract infections
Hematuria and dysuria

55
Q

Cystinuria Management

A

Hydration
Urinary Alkalinizers
Chelating Agents
Crystal Growth Inhibitors

56
Q

Unbranched chain of amino acids - peptide bond

A

Peptides

57
Q

Long unbranched chain of amino acids - peptide bond

A

Polypeptides

58
Q

Molecular weights ranging from about 6000 to about 40,000,000.

A

Proteins

59
Q

Molecular weight of less than about 5000

A

Polypeptides

60
Q

Oligopeptide (10-20 aa)

A

Peptides

61
Q

antidiuretic hormone, Nonapeptide

A

Vasopressin

62
Q

Enhances contraction of smooth muscle cells: wall of the uterus, Stimulates milk ejection from the mammary glands via mechanical stimulus, Nonapeptide

A

Oxytocin

63
Q

Synthetic oxytocin

A

Pitocin

64
Q

Binds to receptor sites to reduce pain body’s natural painkillers; Produced by the brain, Pentapetide

A

Enkephalins

65
Q

Action of narcotic analgesics such as __________ and __________ is based on their binding at the same receptor sites in the brain

A

morphine; codeine

66
Q

Enkephalins Role

A

memory and learning,
control of body temperature,
sexual activity, and
mental illness

67
Q

Regulator of oxidation–reduction reactions, protect cellular contents from oxidizing agents, Glu–Cys–Gly (tripeptide)

A

Glutathione

68
Q

Highly reactive forms of oxygen

A

peroxides and superoxides

BIOCHEMISTRY LEC (6 decks)

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