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Integumentary System > Defects In Metabolism Of AAs > Flashcards

Defects In Metabolism Of AAs Flashcards

1
Q

3 steps of AA and nitrogen metabolism

A

1) removal of a-amino group (NH3)
2) production of urea
3) various metabolic pathways

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2
Q

Glucogenic amino acids

A

AAs that can be broken down in the TCA cycle

Alanine

Arginine

Asparagine

Aspartate

Cysteine

Glutamate

Glutamine

Glycine

Proline

Serine

Valine

Histidine

Methionine

Threonine

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3
Q

Ketogenic amino acids

A

Cant be used in TCA cycle and can only be used for ketonebody production

Leucine = gets broken down to HMG CoA directly

Lysine = gets broken down to acetyl CoA and then HMG CoA overtime

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4
Q

Glucogenic and ketogenic AAs

A

Can be used either for TCA cycle and energy directly by producing NADH and FADH2
Or can be used to create ketone bodies

Tyrosine

Isoleucine

Threonine

Phenylalanine

Tryptophan

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5
Q

Nonessential AAs

A

Alanine

Arginine

Asparagine

Aspartate

Cysteine (requires methionine groups

Glutamate

Glutamine

Glycine

Proline

Serine

Tyrosine

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6
Q

What are the two functions of vitamin B12 as it pertains to AA synthesis

A

1) synthesis of methionine from homocysteine

2) transformation of methylmalonyl CoA -> Succinyl CoA in odd numbered FA degreadation

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7
Q

S-adenosylmethionine (SAM)

A

Is used in methylation of precursor androgen production as well as melatonin and creatine

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8
Q

Folate trap in vitamin B12 Deficency

A

Caused by N5-methyl form of THF in vit. B12 dependent methylation of homocysteine not being able to turn into other THF forms
- this prevents the body from using folate in any way and instead it accumulates

Therefore vitamin B12 deficiency = decreased purine and TMP synthesis as well as THF
- megaloblastic anemia

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9
Q

Hyperhomocystinuria

A

Caused by deficiencies in either Vit B6 or B12 (PLP)

Either or will cause build up of homocysteine (Hcy) since it cant be converted to methionine

High levels of Hcy promotes oxidative damage and inflammation which can lead to occlusive vascular diseases independently
- cardiac and neurological diseases

also if occurs in pregnant patients = neural tube defects (since patient also has low levels of folate

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10
Q

Phenylketonuria (PKU)

A

Either classic (deficiency of Phenylalanine hydroxylase (PAH) (98%) or deficiency of BH4 enzyme (2%)

BOTH Causes a build up of phenylalanine because phenylalanine cant be converted to TYROSINE (Deficency)

  • instead it is shunted into phenylpyriuavte and eventually to phenyllactate and phenylacetate acids (both phenylketones)
  • benign = 2-10 mgldL in blood
  • mild = 10-20 mg/dL in blood
  • severe = > 20 mg/dL in blood

Symptoms
- hyperpheylanemia and lowered catecholamines and melanin in the body
- high levels of phenylketones in blood and urine (urine produces a very musty odor)
- CNS manifestations (toxin accumulation)
- hypopigmentation (fair hair and white with blue eyes)
- GI symptoms (toxin accumulation)
(Often shows misdiagnosis of pyloric stenosis at prenatal screening)

Treatment = dietary restriction of phenylalanine for life

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11
Q

What is the normal metabolism of phenylalanine?

A

Gets converted to tyrosine and then produces one of:

  • tissue proteins
  • melanin
  • catecholamines
  • fumarate and acetoacetate
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12
Q

BH4 deficiency in hyper phenylketonuria

A

Helps reverse some of the early CNS symptoms if supplementation of BH4 is given while also restricting phenylalanine
- but response is unpredictable

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13
Q

Deficiency of dihydropteridne reductase

A

Deficiency of this enzyme causes decreased serotonin, catecholamines and tyrosine levels

Shows similar to hyper phenylalaninemia

Absolutely requires BH4 replacement but is variable with its effectiveness

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14
Q

What is the #1 AA required for melanin production

A

Tyrosine

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15
Q

Pheomelanin

A

Is yellow red alkali soluble melanin subtype

Formed with tyrosine and cysteine metabolism and use

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16
Q

Menkes disease

A

Mutations in the ATP7A gene which prevents copper transporter and use of copper properly

Symptoms:

  • brittle fragile and kinky hair
  • very light skin color and blue eyes
  • hypotonia
  • intellectual disability
17
Q

Oculocutaneous Albnism

A

Is always caused by absence of tyrosinase enzymes

  • subtype A = complete absence and worse outcomes (40%)
  • subtype B = partial absence and better outcomes (60%)

Both of these produce albinism due to the inability or very reduced rates of melanin production

  • all patients have increased risk of skin cancer
  • subtype A = will be very pale with red eyes and silver eyebrows
18
Q

Alkaptonuria

A

Deficiency of homogentisate oxidase enzymes.

  • produces excess homogentisate acid since it cant be broken down to maleyacetoacetate and ultimately furmarate
  • homogentisate isnt overtly toxic but can cause issues

Symptoms:

  • causes patients urine to turn black because oxidation of homogentisic acid occurs
  • cartilage turns black
  • can develop severe arthritis so need to be careful and treat appropriately

Treatment = diets low in protien

19
Q

Tyrosinemia Type 1

A

Defects in fumarate-acetoacetate hydrolase enzymes
- prevents fumarate production and causes buildups of fumarylacetoacetate which if not broken down is toxic

Severely toxic and causes damage to kidney, lover and nervous systems

Treatment = diet low in Phe and Tyr
- also give Nitisinone (NTBC) which inhibits tyrosine to fumarylacetate

20
Q

Methylmalonic acidemia

A

Caused by deficiency in methylmalonyl CoA mutatase or adenosylcobalamin

Produces increased levels of methylmalonic acid in blood since you can’t produce succinyl CoA from the acid
- produces metabolic acidosis and developmental disorders

21
Q

Cystathioninuria

A

Accumulation of cystathionine occurs due to a deficiency of cystathionase

This condition is benign

22
Q

Homocystinuria

A

Caused by a deficiency in cystathionine synthase enzymes

Causes accumulation of homocysteine occurs in the urine and blood
- methionine is also increased whereas cysteine is low

Symptoms:

  • skeletal abnormalities
  • increases in clotting risks
  • lens dislocation**
  • intellect disability
23
Q

Maple syrup disease

A

Caused by a deficiency in BCKD enzymes

Causes build up of isoleucine in urine and blood, leucine and valine as well

Symptoms: 
Feeding issues 
- vomiting 
- ketoacidosis 
- neurological issues 
- coma (caused by leucine levels getting dangerously high)

Two forms

  • classic = no BCKD present and is lethal in early childhood if not aggressively treated
  • variant forms = 30% of normal activity is present of BCKD. Symptoms are milder and show up later in infancy

Integumentary System (29 decks)

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