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CMBM 3 > Enzyme Deficiencies > Flashcards

Enzyme Deficiencies Flashcards

1
Q

What is the causative enzyme for PKU (phenylketonuria)?

A

phenylalanine hydroxylase (PAH)

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2
Q

Which metabolic pathway does Phenylalanine hydroxylase act in?

A

Amino Acid metabolism

- responsible for converting phenylalanine to tyrosine

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3
Q

What is an inborn error of metabolism?

A

general term for diseases caused by mutations to genes involved with metabolic pathways

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4
Q

What precursor builds up in PKU?

A

phenylalanine which then turns to phenylpyruvic acid

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5
Q

How do you treat PKU?

A

keep on a strict diet low in phenylalanine

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6
Q

What enzyme is deficient in Oculocutaneous Albinism?

A

tyrosinase - necessary for formation of melanin

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7
Q

Because of the deficiency of tyrosine in PKU pateints, how to they tend look?

A

blond hair

blue eyes due to deficiency of melanin

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8
Q

Lack of pigment in Oculocutaneous Albinism, leads to what clinical symptoms?

A
  • poor visual acuity
  • nystagmus (pendular eye movement)
  • underdeveloped fovea
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9
Q

What enzyme is deficient in Maple Syrup Urine Disease?

A

branched-chain ketoacid decarboxylase

Maple trees have branches.

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10
Q

What is the result of Maple Syrup Urine Disease?

A

Valine (val), leucine (leu) and isoleucine (ile) are excreted in the urine

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11
Q

What symptoms are present in the first week if newborns have Maple Syrup Urine Disease?

A

vomiting, alternating tone

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12
Q

What is the treatment for Maple Syrup Urine Disease?

A

dietary restriction of val, leu and ile

still susceptible to deterioration

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13
Q

What is the most common carbohydrate metabolism disorder?

A

Glucose-6-phosphate dehydrogenase deficiency

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14
Q

The glucose-6-phosphate dehydrogenase is responsible for what? pathway?

A

oxidative steps of the pentose phosphate pathway

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15
Q

What inheritance pattern is Glucose-6-phosphate dehydrogenase deficiency?

A

x-linked recessive

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16
Q

Glucose-6-phosphate dehydrogenase deficiency leads to reduced ability to produce _________?

A

NADPH (potent reducer used by cells to protect against oxidative damage)
-pentose phosphate pathway

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17
Q

Which cell type is most affected by Glucose-6-phosphate dehydrogenase deficiency? Why?

A

RBC no nucleus to provide other reducing sources
susceptible to oxidative damage

-results in anemias

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18
Q

What populations are more likely to be affected by Glucose-6-phosphate dehydrogenase deficiency?

A

African
Asian
Middle Eastern
Mediterranean

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19
Q

What are the three main sources for oxidative assaults that would cause symptoms of Glucose-6-phosphate dehydrogenase deficiency?

A

INFECTION - cold, flu, sinus infections
DRUGS - NSAIDs, quinolones, sulfa drugs, Tylenol, naphthalene, artificial food coloring
FOOD - fava beans and other legumes, sulfites, menthol-containing foods (toothpaste, mouthwash)

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20
Q

Acute oxidative damage from Glucose-6-phosphate dehydrogenase deficiency can lead to hemolytic anemia which presents with?

A 
paleness
jaundice
dark urine
fatigue
shortness of breath/rapid heart rate
splenomegaly
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21
Q

What treatments are available for Glucose-6-phosphate dehydrogenase deficiency?

A

dietary restriction

drug restriction

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22
Q

Galactosemia is due to a deficiency is what enzyme?

A

galactose-1-phosphate uridyl transferase

involved with breakdown of dietary sugar galactose

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23
Q

What are the symptoms of galactosemia?

A

newborns present with vomiting, lethargy, failure to thrive, and jaundice within 2 weeks

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24
Q

If untreated, galactosemia can lead to what?

A

mental retardation
cataracts
liver cirrhosis

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25
Q

What treatments are available for galactosemia?

A

feed formulas lacking in milk sugars (galactose and lactose)

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26
Q

Hereditary Fructose Intolerance results from deficiency in what enzyme?

A

fructose-1-phosphate aldolase (involved in breakdown of dietary fructose)

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27
Q

When does Hereditary Fructose Intolerance present and what are the symptoms?

A

presentation age varies (depends on when foods with fructose are introduced)
Symptoms: minimal to severe
Severe: failure to thrive, vomiting, jaundice and seizures

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28
Q

How would you treat Hereditary Fructose Intolerance?

A

fructose food restriction

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29
Q

List the 4 glycogen storage diseases affecting the liver.

A 
Von Gierke (breakdown)
Cori (breakdown)
Anderson (synthesis)
Hepatic phosphorylase deficiency (breakdown)
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30
Q

Which enzyme is deficient in Von Gierke?

A

glucose-6-phosphate

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31
Q

Which enzyme is deficient in Cori disease?

A

amylo-1,6-glucosidase (debrancher enzyme)

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32
Q

Which enzyme is deficient in Anderson disease?

A

glycogen brancher enzyme (synthesis of glycogen)

4,6 transferase

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33
Q

What is the inheritance pattern for hepatic phosphorylase deficiency?

A

autosomal

x-linked

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34
Q

How does Von Gierke present?

A

hepatomegaly
hypoglycemia

infants-sweating, fast HR

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35
Q

How does Cori disease present?

A

hepatomegaly

muscle weakness

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36
Q

How does Anderson present?

A

hypotonia

abnormal liver function w/i first year&raquo_space;>liver failure

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37
Q

How does hepatic phosphorylase deficiency present?

A

hepatomegaly
hypoglycemia
failure to thrive

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38
Q

How would you treat Von Gierke disease?

A

frequent feeding to reduce hypoglycemia

avoid fasting

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39
Q

How would you treat Cori disease?

A

frequent feeding to reduce hypoglycemia

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40
Q

How would you treat hepatic phosphorylase deficiency?

A

carbohydrate supplementation

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41
Q

List 2 glycogen storage diseases affecting muscle.

A

Pompe

McArdle

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42
Q

Which enzyme is deficient in Pompe?

A

a-1,4-glucosidase (necessary for glycogen breakdown)

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43
Q

Which enzyme is deficient for McArdle?

A

muscle phosphorylase (necessary for breakdown of muscle glycogen during exercise)

44
Q

How does Pompe present?

A

in infancy with hypotonia, delay in gross motor milestones

enlarged heart
cardiac failure within 2 years

45
Q

What treatment is available for Pompe?

A

no current treatment

-experimenting with enzyme replacement therapies

46
Q

How does McArdle present?

A

presents in ADOLESCENSE with muscle cramps during exercise

47
Q

What treatment is available for McArdle?

A

no current treatment

48
Q

List 2 steroid metabolism disorders.

A

Congenital Adrenal Hyperplasia (CAH)

Androgen Insensitivity Syndrome

49
Q

What is the most common cause of ambiguous genitalia in female newborns?

A

Congenital Adrenal Hyperplasia (CAH)

50
Q

In 90% of cases Congenital Adrenal Hyperplasia (CAH) is due to what enzyme deficiency?

A

21-Hydroxylase

51
Q

25% of Congenital Adrenal Hyperplasia (CAH) cases have the salt-losing form. How does it present?

A

2-3 weeks of life with circulatory collapse

  • hypernatremia
  • hyperkalemia
52
Q

What is the inheritance pattern of Congenital Adrenal Hyperplasia (CAH)?

A

autosomal

  • seen in males
  • ambiguous genitalia in females
53
Q

Affected females are virilized due to accumulation of ?

A

adrenocorticosteroids (many have testosterone-like functions)

54
Q

How are Congenital Adrenal Hyperplasia (CAH) infants treated?

A

replacement cortisol for life (with increases given during times of stress)

**fludrocortisone is given as well in salt-losing forms

*plastic surgery for females

55
Q

Androgen insensitivity syndrome is due to defect in what?

A

defective testosterone receptor

normal levels of testosterone are produced but due to lack of receptors genes cannot be expressed

56
Q

When is Androgen insensitivity syndrome identified?

A

not identified until lack of menses

in cases of “inguinal” hernia which is actually internalized testes

57
Q

What is the inheritance pattern of Androgen insensitivity syndrome ?

A

x-linked recessive

46 XY

58
Q

List a lipid metabolism disorder.

A

Familial Hypercholesterolemia

59
Q

What is the inheritance pattern for Familial Hypercholesterolemia?

A

autosomal dominant single-gene

**associated with high morbidity and mortality

60
Q

How can Familial Hypercholesterolemia present in childhood?

A

xanthomata - buildup of cholesterol under the skin

61
Q

How would you treat Familial Hypercholesterolemia?

A 
dietary restriction
statin drugs (HMG-CoA reductase inhibitors)
62
Q

What is the result of the mutation in Familial Hypercholesterolemia?

A

problems with the LDL receptor

63
Q

What are the 4 main classes of problems with the receptor?

A
  1. Reduced/defective biosynthesis
  2. Reduced/defective transport
  3. Abnormal binding of LDL by the receptor
  4. Abnormal internalization of the receptor
64
Q

What are the two lysosomal storage disorders?

A

Mucopolysaccharidosis

Sphingolipidosis

65
Q

What is the most common Mucopolysaccharidosis?

A

Sanfilippo syndrome

66
Q

How does Sanfilippo Syndrome (Mucopolysaccharidosis) present?

A

2nd year of life - coarsening of features, skeletal changed, progressive intellectual loss, seizures and death in early adult life

67
Q

What enzyme is deficient in Mucopolysaccharidosis?

A

any one of four enzymes involved in degradation of heparin sulfate

68
Q

What is the treatment for Mucopolysaccharidosis?

A

no standard treatment

69
Q

What are the two most common Sphingolipidosis disorders?

A

Tay-Sachs

Gaucher

70
Q

How is Sphingolipidosis characterized?

A

inability to degrade sphingolipids

71
Q

What is the result of inability to degrade spingolipids?

A

accumulation of lipids or glycolipids, especially in brain, liver and spleen

72
Q

If the CNS is involved in Sphingolipidosis, what is the progression of the disease?

A

mental deterioration
seizures
death in childhood

73
Q

What enzyme is deficient in Tay Sachs?

A

B-hexosaminidase

results in accumulation of sphingolipid GM, ganglioside

74
Q

What population has a high incidence of Tay-Sachs?

A

Ashkenazi Jews

75
Q

How does Tay-Sachs present?

A

at 6 months with poor feeding, lethargy, eventual developmental regression and feeding difficulties

Death usually occurs by 3 due to respiratory infections

(less severe forms are reported)

76
Q

How is diagnosis of Tay-Sachs aided?

A

cherry red spot in center of macula fundus

77
Q

What is the treatment for Tay-Sachs?

A

no current treatment

78
Q

What enzyme is deficient in Gaucher?

A

glucosylceramide B-glucosidase

79
Q

What population has a high incidence of Gaucher?

A

Ashkenazi Jews

80
Q

What is the most common Sphingolipidosis?

A

Gaucher

81
Q

Describe Type 1 Gaucher.

A 
adult onset (most common form)
pain in limbs, joints and/or trunk
tendency to bone fractures
hepatomegaly
mild anemia
some changes in vertebrae 
CNS is spared
82
Q

Describe Type 2 Gaucher.

A 
presents between 3-6 months
CNS involvement
Failure to thrive
hepatosplenomegaly
developmental regression
neurological deterioration
**seizures
Death by age 2 due to repeated respiratory infections
83
Q

Describe Type 3 Gaucher.

A

presents in childhood with intermediate symptoms

84
Q

How would you treat Gaucher?

A

Type 1/3
analgesics for pain management
Splenectomy in some cases
Cerezyme (enzyme replacement therapies)

Type 2
no known treatment

85
Q

List two nucleic acid disorders.

A

Lesch Nyhan Syndrome

Adenosine Deaminase Deficiency

86
Q

What enzyme is deficient in Lesch Nyhan?

A

HGPRT (hypoxanthine guanine phosphoribosyltransferase)

- involved in salvage pathway of purine

87
Q

What product builds up due to inability to salvage purines?

A

hypoxanthine
guanine
PRPP

**also causes a feed forward reaction to de novo synthesis

88
Q

Increased levels of PRPP causes activation of what pathway?

A

de novo synthesis of purines

-levels can be 200x higher

89
Q

Breakdown of excess purines will result in accumulation of ?

A

uric acid

90
Q

What results from too much uric acid?

A

crystals form»>gout

“sand in diaper”

91
Q

What are the symptoms of Lesch Nyhan?

A

uncontrolled movements
spasticity
mental retardation
compulsive self-mutilation

92
Q

What is the treatment for Lesch Nyhan?

A

Allopurinol, but does NOT seem to treat the neurological symptoms

93
Q

What enzyme is responsible for 15% of all cases of SCID (Severe combined immunodeficiency syndrome)?

A

adenosine deaminase

94
Q

How does adenosine deaminase deficiency present?

A

in infancy with recurrent bacterial and viral infections

**if untreated can lead to death

95
Q

What is adenosine deaminase responsible for converting?

A

AMP to IMP in the purine salvage pathway

96
Q

What immune deficiencies are seen in patients with adenosine deaminase deficiency?

A

deficient in T and B cells leaving them without a functional immune system

97
Q

What is the treatment for adenosine deaminase deficiency?

A

no current treatment

clinical trials under way using gene therapy to treat SCID

98
Q

What is a porphyrin?

A

ringed structures that can chelate metal

99
Q

List two Porphyrin Metabolism Disorders?

A

Acute Intermittent Porphyria

Congenital Erythropoietic Porphyria

100
Q

What enzyme is deficient in Acute Intermittent Prophyria?

A

uroporphyrinogen I synthase

  • used in bone marrow heme synthesis
  • leads to increased excretion of the precursors porphobilinogen and delta-aminolevulinc acid in urine
101
Q

What are the symptoms of Acute Intermittent Prophyria?

A 
abdominal pain
weakness
vomiting
mental and emotional disturbances
anemia
some:
hallucinations
coma
102
Q

What can precipitate Acute Intermittent Prophyria?

A

use of certain drugs
steroids
anticonvulsants
barbituates

103
Q

What enzyme is deficient in Congenital Erythropoietic Porphyria?

A

uroporphyrinogen III synthase

- in bone marrow heme synthesis

104
Q

What are the symptoms of Congenital Erythropoietic Porphyria?

A
  • extreme photosensitivity
  • hemolytic anemia - require blood transfusions and splenectomy
  • red/brown discoloration of teeth, fluoresce red under UV light
105
Q

6 month old is brought in for recurrent respiratory infection. The child seems to be moving backwards developmentally and has a history of seizures. Testing reveals a deficiency in _______ , leading to a diagnosis of _____.

A

glucosylceramide b-glucodidase

Gaucher

CMBM 3 (28 decks)

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