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Nitrogen metabolism Flashcards

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USMLE® Step 1 flashcards
1
Q

Phenylalanine hydrolase

A
  • PAH
  • Phenylalanine + tehtrahydrobiopeterin (BH4) (cofactor)–>Tyrosine + dihydroiopeterin (BH2)

Defect in PKU I (classic PKU)

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2
Q

PKU I

A
  • defect in phenylalanine hydroxylase
  • can’t convert phenylalanine to tyrosine (tyrosine becomes essential AA)
  • decreased melanin synthesis (from tyrosine)–>decreased pigmentation of skin (phe–|tyrosinase)
  • CNS symptoms: delay in milestones, low IQ (untreated, major IQ reduction in early development); Seizures @ high blood [phe]
  • Phe metabolized to phenylpyruvate, phenylacetate, phenyllactate–>excrete in urine–>mousey odor
  • blood [Phe] elevated

-IQ decreases after cessation of Phe free diet

Treatment:

  • dietary restriction of Phe
  • Sapropterin–>synthetic BH4 (mild or moderate forms of disease) (mutant enzyme with low cofactor affinity)
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3
Q

Sapropterin

A

synthetic tetrahydrobiopterin (BH4)

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4
Q

Maternal PKU syndrome

A

High Phe in mothers is tratogenic–>leads to birth defects

  • microcephaly, mental retardation, congenital heart defects
  • kid isn’t PKU + (ususally heterozygous)
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5
Q

PKU II

A
  • malignant PKU
  • deficiency of diydrobiopterin reductase (BH2/BH4) or BH2 synthesis
  • more severe/worse prognosis than PKU I
  • CNS symptoms worse–>decreased neurotransmitter synthesis (serotonin, dopamine, catecholamines)
  • treatment: Phe restriction, dietary biopterin and precursors of neurotransmitters (blood/brain barrier limits efficacy)
  • elevated Phe and metabolites
  • phenylpyruvic acid in urine leads to mousey odor
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6
Q

dihydrobiopterin reductase

A

Dihydroiopterin (BH2)–>tetrahydrobiopterin (BH4)

deficient in PKU II

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7
Q

Homogentisic acid oxidase

A

Full name homogentisate 1,2-dioxygenase

homogentisic acid—> maleylacetoacetate

used in pathway from tyrosine to fumarate and acetoacetate

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8
Q

Alkaptonuria

A
  • defect in homogentisate 1,2-dioxygenase
  • homogentisic acid–>maleylacetoacetate
  • ^ is a brown pigment
  • relatively benign
  • Ochronosis: homogentisic acid deposits in cartilage and connective tissue–>leads to severe arthritis
  • homogentisic acid is excreted in urine–>brown color on standing (oxidation of homogentisic acid)
  • dietary restriction of Phe and Tyr may reduce deposition
  • bluish-black discoloration of sclera and auriculum)
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9
Q

Tyrosinosis

A
  • Tyrosinemia type I
  • deficinecy of fumarylacetoacetate hydrolase
  • build up of fumaryl acetoacetate leads to kidney and liver damage
  • severe usually fatal
  • cabbage-like odor of urine
  • attempt dietary restriction of Phe and Tyr (difficult b/c both essential and needed for neurotransmitter synthesis)
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10
Q

Fumarylacetoacetate Hydrolase

A

fumarylacetoacetate–>fumarate + acetoacetate

defective in Tyrosinemia Type I

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11
Q

Maple Syrup Urine Disease (MSUD)

A
  • deficiency of branched chain α-ketoacid dehydrogenase (branched chain keto acid–>___acyl-CoA)
  • rare
  • symptoms develp @ 4-7 days
  • presents with poor feeding, vomiting, poor weight gain, increasing lethargy
  • neurological signs (alternating muscular hypotonia and hypertonia, seizures, encepalopathy)
  • ketosis–>maple syrup odor
  • coma and death in early infancy if untreated
  • Treatment: dietary restriction of branched chain amino acids (leu, ile, val)–>all essential, difficult (improves neurological manifestations; dietary supplementation with TPP (vit B1 useful in some pts with low coenzyme affinity)
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12
Q

Branched chain α-ketoacid dehydrogenase

A
  • Requires TPP
  • deficiency causes MSUD
  • branched chain keto acid–> corresponding acyl-CoA
  • paralog of αKgDH, PDH
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13
Q

Methylmalonic Aciduria

A
  • deficiency in Methylmalonyl-CoA Mutase
  • elevated levels of methylmalonic acid (methylmalonic acidemia)
  • metabolic acidosis
  • Methylmalonic Aciduria
  • neurological symptoms: seizures, encephalopathy
  • some pts improve with B12 (cobalmin) supplementation–>those with reduced coenzyme affinity
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14
Q

Methylmalonyl-CoA Mutase

A
  • methylmalonyl-CoA to succinyl-CoA
  • reuqires vit B12 cofactor dervived cofactor-adenosylcobalamin
  • deficiency causes methymalonic aciuria
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15
Q

Homocystinuria/Hyperhomocysteinemia

A
  • group of disorders involving homocysteine metabolism–>commonly Cystathionine β-synthase
  • homocysteine accumulates in connective tissue and disrupts the structure (forms disulfide bridges with collagen cys residues)
  • dislocation of lens (ectopia lentis) after age 3 (and other ocular abnormalities)
  • skeletal abnormalities (childhood osteoporosis)
  • mental retardation
  • premature arterial disease (lipid deposits–>atheromas; lipid oxidation and platelet aggregation–>fibrosis & calcification of atherosclerotic plaques)
  • some pts respond to oral vit B6
  • special diet

-Hyperhomocysteinemia is typically managed with vitamin B6, folic acid, and vitamin B12 supplementation. [3] Taurine supplementation also has been found to reduce homocysteine levels.[4] (http://en.wikipedia.org/wiki/Hyperhomocysteinemia)

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16
Q

Cystathionine β-synthase

A
  • part of transulfuration pathway (methionine to cys)
  • homocysteinine–>cystathionine
  • requires PLP (vit B6)
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17
Q

Fate of homocysteine

A
  • recycled to methionine (required THF and vit B12)
  • sulfur transfered to serine by Cystathionine β-synthase in transulfuration rxn forming cysteine and a carbon skeleton (require B6=PLP), carbons–>Succinyl-CoA (needs B12)
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18
Q

Amino acid pool

A
  • circulating free amino acids
  • sources: dietary, tissue protein catabolism, synthesis of non-essential

Uses:

  • Amnio acid catabolism: ammonia–>urea
  • Carbon skeleton: glucose/lipid synthesis, oxidation in TCA (pyruvate)
  • stynthesize nitrogen containing compounds: creatine, heme, neurotransmitters, purines, pyrimidines, etc
  • build proteins
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19
Q

Essential Amino Acids

A
  • Phenylalanine (F), Valine (V), Tryptophan (W), Threonine (T), Isolucine (I), Methionionine (M), Arginine* (R), Leucine (L), Lysine (K)
  • Arg is essential only during high demand in childhood

The Whole Food Ladder Really Must Have Various Key Ingredients

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20
Q

Conditionally Essential AA

A
  • Cysteine-when met is insufficient
  • Arg-conditional during rapid growth when in high demand
  • Tyrosine: Y and F can be interconverted, one is needed
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21
Q

Protein degredation pathways

A
  • Lysosomal-extracellular or membrane proteins

- ubiquitin/proteasome-proteins made by the cell

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22
Q

Ubiquitin/Proteasome degredation

A
  • used for oxidatively damaged, or denatured proteins

- PEST sequences-rich in pro, blu, ser, and the have short t1/2

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23
Q

Lysosome functions

A
  • normal degredation fo some cellular components
  • material from phagocytosis
  • receptor mediated endocytosis (i.e.: LDL receptor)
  • autophagy
  • extracellular digestion: acrosome, inflammatory processes can cause inappropriate release of lysosomes from WBC’s (i.e.: gout)
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24
Q

Liver in N metabolism

A
  • deamination (AA–>NH3 + carbon skeleton)
  • NH3–>urea (urea cycle)
  • carbon skeleton–>gluconeogenesis, TCA, ketogenesis, probably FA de novo synthesis
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25
Q

Kidney in N metabolsim

A
  • excretes urea from liver in urine
  • excrete NH3 as NH4+ (regulation of acid/base balance; source is gluatmine, glutaminase)
  • excretes uric acid (end product of purine degradation), creatinine (end product of creatine degradation), nitrogenous non-protein substances
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26
Q

Cystinuria

A
  • caused by decreased tubular reabsorption of cystein (and other dibasic aa’s ornitine, arg, lys)
  • inherited deficiency of cystine transporter
  • Cystine excreted in urine
  • Cys precipitates in renal tubules (systine stones)–>cause of renal stones in children
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27
Q

Hartnup’s Disease

A
  • inherited defect in transport of neutral amino acids (ex: tryptophan)
  • decreased absorption and increased excretion (due to decreased reabsorption)
  • Some pts experience niacin def (low protein diet)–>NAD+ deficiency aka pellagra (niacin is usually synthesized from W)
  • 4D’s of Pellagra: diarrhea, dermatitis, dementia, death
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28
Q

Ketogenic Amino acids

A

exlusively: Leu, Lys
also glucogenic: Ile, Phe, Tyr, Trp

Ile, Leu—>acetyl-CoA
Leu, Lys, phe, trp, tyr–>acetoacetyl-CoA

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29
Q

Glucogenic AA

A

everything except Leu and Lys
also Ketogenic: Ile, Phe, Tyr, Trp

*Asn, Asp-->OAA
Phe, Tyr--->fumarate
Ile, Val (branched chain)-->Succinyl-CoA
**Ala-->pyruvate
**Glu, Gln-->α-ketogluterate
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30
Q

ALT

A
  • Alanine aminotransferase/transaminase
  • Requires PLP (B6)

Ala + αKG Pyruvate + Glu

reversable, driven by concentration

-in liver, entrance of asp into TCA, also another enzyme that can interconvert Glu and α-KG

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31
Q

Importance of Alanine

A
  • major transport Amino acid from muscle to liver (glucose/alanine cycle)
  • major precursor of glucose genesis (ALT to pyruvate)
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32
Q

Glucose/Alanine cycle

A

a/k/a Cori Cycle:

  • pyruvate formed in muscle converted to Ala and transported to liver
  • in liver turned back to pyruvate, used as substrate for glugoneogenesis, glucose put back into blood to muscle
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33
Q

Glutamate dehydrogenase

A

Glutamate + NAD+ α-ketogluterate + NH3 + NADH

  • Oxidative deamination/reductive amnination (backwards)
  • Goes forwards in liver to deliver α-ketogluterate to TCA under starvation, also release NH3 for urea cycle

-Goes reverse in peripheral tissues to sequester NH3 for transport to liver for urea cycle when tissue [NH3] is high

1 of 3 enzymes that can incoporate free NH3

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34
Q

AST

A

Aspartate aminotransferase a/k/a serum glutamic oxaloacetic transaminase (SGOT)

Requires PLP (B6)

Aspartate + α-ketogluterate Oxaloacetate + Glutamate

-in liver, entrance of asp into TCA, also another enzyme that can interconvert Glu and α-KG

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35
Q

enzymes that do: α-ketogluterateglutamate

A

ALT, AST, and glutamine transaminase

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36
Q

Glutamine Synthetase

A

Glutamate + NH3 + ATP—->Glutamine + ADP + Pi

  • present in peripheral tissues, especially important in Brain (neurotransmitter synthesis I belive uses many deaminations, maybe) and endothelium of hepatic vein (prevent free NH3 from getting to the rest of the body)
  • 1 of 3 enzymes that can incorporate free NH3
  • Glutamine used to transport NH3 to liver
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37
Q

Glutaminase

A
  • Glutamine + H2O—>Glutamate + NH3
  • present in renal tubules and liver
  • renal: used to maintain acid/base balance, excrete as NH4+
  • liver: NH3 goes into urea cycle, glutamate gives off another NH3 using GDH, and α-KG goes into TCA
38
Q

Asparagine Synthetase

A

Aspartate + Glutamine + ATP —->Asparagine + AMP + PPi

-uses glutamine as source of Nitrogen

39
Q

Asparaginase

A

Asparagine + H2O —> Aspartate + NH3

  • ASP is used to make OAA by AST for TCA/gluconeogenesis
  • NH3 to Urea cycle
  • Used to treat leukemia pts (leukemia cells need Asn, reduce availability to limit growth)
40
Q

General transaminase rxn

A

α-Amino acid + α=ketogluterate α-keto acid + Glutamate

  • All transaminases require PLP (vitamin B6)
  • α-Kg is usually the amino acceptor but there are exceptions
  • glutamate becomes important N carrying group
41
Q

Ammonia transport

A
  • Alanine: from muscle; transamination of pyruvate buy ALT
  • Glutamine: most tissues; from glutamine by glutamine synthase (glutamate from protein breakdown, glutamate dehydrogenase, ALT, AST)
42
Q

NH3 formation in liver

A
  • Glutamate: Glutamate dehydrogenase, get NH3
  • Glutamine: Glutaminase forms NH3 and glutamate
  • Alanine and other AAs: transaminases (using PLP) form glutamate
43
Q

Sources of N in urea cycle

A
  • 1st from NH3

- 2nd from Asp (remember asp forms OAA by AST using Glu as N source)

44
Q

Urea cycle enzymes in order

A
  1. Carabmoylphosphate synthetase I, CPS-1 (mito) (rate limiting step)
  2. Ornithine Transcarbamyolase, OTC (mito)
  3. Arginosuccinate Synthetase, ASS (cyto)
  4. Arginosuccinate Lyase, ASL (cyto)
  5. Arginase, ARG1 (cyto)
45
Q

Urea cycle intermediates in order

A

Starting material: HCO3-, NH4+, 2 ATP

  1. Carbamyl phosphate
  2. Citrulline (+Aspartate)
  3. Argininosuccinate
  4. Arginine (+fumerate)
  5. Ornithine (+Urea)
46
Q

CPS-I

A

Carbamoyl Phosphate Synthetase I
HCO3- + NH4+ 2 ATP —> Carbamyl Phosphate + 2 ADP + Pi

  • 1st and rate limiting step
  • Mitochondria
  • N-acetylglutamate is required as an absolute activator
  • 1 of 3 enzymes that incorporate free NH3
47
Q

OTC

A

Ornithine Transcarbamyolase
Carbamyl Phosphate + Ornithine –> Citrulline + Pi

  • 2nd step
  • mitochondria
48
Q

ASS

A

Argininosuccinate Synthetase
Citrulline + ATP + Aspartate –> Argininosuccinate + AMP + PPi

  • 3rd step
  • cytosol
49
Q

ASL

A

Argininosuccinate lyase
Argininosuccinate –> Arginine + Fumarate

  • 4th step
  • cytosol
  • Fumerate my enter TCA or be oxidized back to oxaloacetate
50
Q

ARG-I

A

Arginase
Arginine–>Urea + Ornithine

  • 5th step
  • cytoplasm
51
Q

Enzymes that incorporate free NH3

A

Glutamate Dehydrogenase, Glutamine synthase, Carbamyl Phosphate Synthase I

52
Q

Energy used in urea cycle

A

4 high energy bonds: 2 ATP–>ADP, 1 ATP–>AMP

53
Q

Inherited Urea Cycle disorders

A
  • accumulation of substrates of deficient enzyme (any complete absence would be miscarriage)
  • Increased blood ammonia (hyperammonemia) and elevated blood glutamine
  • urea formation decreased altough levels will be approximately normal
  • Hyperammonemia symptoms appear in first few days: lethargy, irritability, feeding difficulties
  • nerurological symptoms if untreated i.e.: seizures, mental retardation
  • CPS1 and OTC (first two) are most severe
54
Q

Hyperammonemia Type I

A
  • Carbamoyl-phosphate synthetase deficiency
  • hyperammonemia
  • neurological symptoms
  • elevated glutamine
  • sometimes respons to Arg intervention (arg stimulates NAG formation, might stimulate CPS-I)
55
Q

Hyperammonemia Type II

A
  • Ornithinie Transcarbamyolase deficiency
  • X-linked (more in male, more severe in male)
  • most common
  • hyperammonemia
  • increased orotic acid in urine and serum (orotic aciduria/emia) (mostly worry about the urine)
  • diagnose by elevated serum ammonia and urine orotic acid
56
Q

Citrullinemia

A
  • Argininosuccinate synthetase deficiency
  • diagnosis: hyperammonemia, very increased citrulline levels (blodd and urine)
  • treatment may include arginine–>enhance urinary citrulline excretion. drive urea cycle with more substrate
57
Q

Argininosuccinic aciduria

A
  • Argininosuccinate Lyase deficiency
  • hyperammonemia
  • diagnosis: argininosuccinate elevated in plasma and CSF, increased argininosuccinate levels in urine, moderately high citrulline
  • can sometimes treat with arginine–>enhance urinary excretion, push urea cycle with substrates/intermediates
58
Q

(Hyper)argininemia

A
  • Arginase deficiency
  • increased arginine levels
  • diagnosis: high serum arg and NH3 (NH3 not as high as other UCDs)
  • restrict diet to essential amino acids excluding arginine
  • frequently adult onset: neurological problems
59
Q

Treatment of hyperammonemia

A
  • dialysis-emergency
  • benzoic acid–>benzoyl-CoA + glycine–> Hippurate (remove 1 mol N per mol of drug)
  • low protein/high carb diet (minimize N intake)
  • avoid stresses leading to catabolic state
  • long term: liver transplant
  • phenylbutrate–>phenylacetate–>phenylacetyl-coA–>phylacetylglutamine (2 N per molecule removed in urine)
60
Q

Phenylbutrate

A

phenylbutrate–>phenylacetate–>phenylacetyl-coA–>phylacetylglutamine (condense with glutamine)

-2 N per molecule removed in urine

61
Q

benzoic acid

A

benzoic acid–>benzoyl-CoA + glycine–> Hippurate (remove 1 mol N per mol of drug)

62
Q

Fate of Urea

A
  • transported to kidney, eliminated in urine
  • 25% degraded by bacterial ureases in gut–>ammonia returns to circulation (85% portal, 25% systemic) and must go through urea cycle again
  • kidney failure–>elevated blood urea nitrogen (BUN) wherease UCD leads to elevated NH3
63
Q

Aquired hyperammonemia

A
  • liver disease (viral or drug induced hepatitis, alcoholic cirrhosis, I think some GSDs)
  • cirrhosis–>portocaval anastamosis leads to higher [NH3] in systemic circulation b/c blood doesn’t go through liver–>neurotoxicity

Treatment:

  • low protein/high carb diet (less N ingested)
  • Lactulose-disaccharide, resistant to digestion–>used by intestinal flora–>produce lactic acid–>neutralized by NH4+–>N excreted in feces
  • Neomycin (or other antibiotic)–>kill your flora, less urease
  • other treatments
64
Q

Hypothesises for NH3 neurotoxicity:

A

Energy and osmotic effect:
α-ketogluterate–>glutamate requires reducing equivalents and consumes TCA cycle intermediates–>less TCA–>less ATP synthesis–>reduced K+/Na+ ATPase–>up osmotic pressure–>neuronal death

Neurotransmittler effect:
Glutamate to glutamine (using glutamine synthase–>high serum glutamine)–>reduced glutamate and GABA (made from glutamate in brain) (both reduced at high NH3) (GABA is an inhibitory NT, GLU is a major excitatory NT)

65
Q

Tyrosine hydroxylase

A

Tyrosine—>L-DOPA (dihydroxyphenylalanine)

requires tetrahydropiopterin (BH4) (–>BH2)

66
Q

DOPA Decarboxylase

A

L-DOPA—>Dopamine + CO2

Requires PLP (vit B6)

67
Q

Dopamine β-decarboxylase

A

L-DOPA + O2 —>Norepinepherine + H2O

Requires Vitamin C (absorbic acid—>dehydroxyascorbic acid)

68
Q

Phenylethalnolamine-N-methyltransferase

A

Norepinepherine + S-adenosyl-methionine (SAM)–>Epinepherine + homocysteine

69
Q

Parkinson’s Disase

A
  • neurodegenerative disorder
  • loss of dopamine producing cells
  • movement disorders: spasticity, tremors, loss of memory, mood distrubances, postural instability
  • improve with administration of L-DOPA–>converted to dopamine in brain (inc [substrate])
  • Inhibit peripheral dopamine formation (so that L-DOPA is use preferentially in brain)–>DOPA decarboxylase inhibitor (presumably can’t cross blood brain barrier)
70
Q

Norepinephrine and Epinephrine degredation

A

2 enzymes: Monoamine Oxidase A (requires FAD), then Catechol-O-methyltransferase (COMT, requires S-adenosyl-methionine)
(Nor)epinephrine—->——>Vanillyl Mandelic Acid (VMA)

VMA excreted in urine, used to measure (nor)epinepherine levels

71
Q

Dopamine Degredation

A

2 Enzmes:
Monoamine oxidase (A or B don’t matter) (FAD)
Catechol-O-methyltransferase (COMT) (SAM)

Dopamine—>—>homovanillic acid (HVA)

-HVA in urine, presumably can beassayed for dompamine levels

72
Q

Pheochromocytoma

A
  • tumor of adrenal gland medulla leading to overprocudtion of catecholamines
  • predominant symptoms: headache, sweating, tachycardia
  • also palpitations, anxiety, panic attacks, hypertension
  • symptoms are episodic
  • Diagnosis: high urinary VMA and catecholamines–>24 hr measurement during symptom episode
73
Q

Serotonin synthesis and degradation

A

Tryptophan—>5-hydroxytryptophan (5-HTP)—–>Serotonin (5-hydroxytryptamine)—–>5-hydroxyindole acetic acid (5-HIAA)

  1. Tryptophan Hydroxylase (BH4)
  2. (Aromatic L-) Amino acid Decarboxylase (PLP/B6)
  3. MAO-A (FAD)

Produced in gut, platelets and CNS

74
Q

Tryptophan Hydroxylase

A

Tryptophan—->5-hydroxytryptophan

requires BH4–>BH2

75
Q

Aromatic acid decarboxylase

A

5-hydroxytryptophan—>Serotonin
-PLP

Wikipedia:
Full name: Aromatic L-amino acid decarboxylase
Same as Dopa decarboxylase
L-DOPA to dopamine - a neurotransmitter
5-HTP to serotonin (5-HT) - also a neurotransmitter
tryptophan to tryptamine - a precursor to many alkaloids found in plants and animals
Phenylalanine to phenethylamine - a trace neurotransmitter

76
Q

Carcinoid Syndrome

A
  • tumor of serotonin producing cells in GIT (APUD cells)
  • Cutaneous flushing
  • gastrointestinal hypermotility–>diarrhea
  • bronchospasm
  • increase 5-HIAA in urine
77
Q

Melanin

A

-derived from Serotonin (which was derived from trypophan)

78
Q

Tetrahydrobiopterin

A
  • BH4
  • required cofactor in many amino acid hydroxylations
  • Penylalanine/tyrosine/tryptophan hydroxylases
  • Also Nitric oxide synthase (NOS) and Alkylglycerol monooxygenase
79
Q

Tetraydrobiopterin Deficiency

A
  • caused by deficiency of dihydrobiopterin synthase of BH2 reductase
  • hyperphenylalaninemia and decreased synthesis of neurotransmitters (catecholamines and serotonin)
  • delayed mental development and seizures
  • Managed with dietary BH4, dietary neurotransmitter precursors, restriction of Phe
80
Q

Glutamate Decarboxylase

A

Glutamic Acid—>Gamma amino butyric acid

requires PLP

81
Q

GABA

A
  • inhibitory neurotransmitter in CNS

- formed from glutamate by glutamate decarboxylase

82
Q

Histidine Decarboxylase

A

Histidine——>histamine
PLP
(Sobering doesn’t care if we know something this simple)

83
Q

Histidine

A
  • synthesized from Histidine by histidine decarboxylase (with PLP) in Mast Cells
  • vasodialator
  • antihistimine drugs reduce adverse affects of allergic reactions
  • antihistimies are typically receptor antagonists or otherwise interrupt signalling pathway, do not normally interere in synthesis
84
Q

Creatine

A
  • reservoir of high energy bonds in muscle
  • synthesized from Arg, Gly, and SAM
  • accepts Pi groups from ATP when resting (Creatine Kinase)
  • dontates Pi to ADP when contracting (Creatine Kinase)
  • spontaneously converted to Creatinine–>end product of creatine metabolsm
85
Q

Creatinine

A
  • spontaneously formed from Creatine–>end product of creatine metabolsm, eliminated in urine
  • dependent on muscle mass of individual
  • serum creatinine used as marker of kidney fxn–>not efficiently filtered in renal failure, serum creatinine rises
86
Q

Creatine Kinase

A
  • or Creatine Phosphokinase
  • creatine + ATPcreatine-Pi + ADP
  • total CK/CK-MB used as marker of MI
87
Q

Nitric Oxide

A
  • Synthesized from Arginine–>NO⋅ + citrulline
  • Nitric Oxide Synthase requires heme, NADPH, FAD, FMN, BH4
  • made in enothelial cells
  • local vasodialation
  • nitroglycerin–>converted to NO⋅ causes vasodialiation of coronary blood vessels–>improvement of blood flow to dart
  • short half life
  • 2nd messenger of cGMP pathway (activates soluble guanylate cyclase)
88
Q

Albinism

A
  • caused by deficiency of Tyrosinase (oxidase)
  • defcient conversion of tyrosine to melanin
  • group of disorders (partial to complete)-severe form affects eyes (oculocutaneous albinism)
  • lower visual acuity adn photophobia
  • light colored skina dn hair
  • increased risk of sun damage from sun and skin cancer
89
Q

Melanin

A
  • herogenous group of tyrosine derived pigments

- tyrosinase is rate limiting step in synthesis

90
Q

Thyroid hormone

A
  • T3 or T4
  • formed on tyroglobulin protein
  • tyrosine acceps iodione (iodination)
91
Q

Glutathione

A
  • tripeptide made from glutamate, cysteine, and glycine
  • reducing agen
  • detox of H2O2
  • protects from membrane damage, mainatin free -SH ends of proteins
  • conjugated to drugs to make them H2O soluble
  • cofactor in some enzymatic rxns (glutathione peroxidase)
  • aid in rearrangment of disulfide bonds
  • protects RBC from oxidative stress
  • glutathione reductase needs NADPH (from PPP)

Medical Biochemistry (24 decks)

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