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03 Biochemistry > 17 Aminoacid Metabolism > Flashcards

17 Aminoacid Metabolism Flashcards

1
Q

Hartnup Disease mechanism and symptoms

A

Defective transport in intestine and kidney of large neutral aminoacids
including Trp
Pellagra like symptoms: Dermatitis, Dementia, Diarrhea

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2
Q

mechanism and symptoms Cystinuria

Treatment

A

Defect transport in intestine and Kidney of Basic aminoacids: Lysine and arginine
Cystine: Disulfide dimer of cystein > insoluble in water cause Stone & Infecton

Treatment with Acetazolamide ↑urinary pH become more soluble or penicillamine to combine it

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3
Q

hyperammonemia results

A

Toxic effects onthe brain (cerebral edema, convulsions, coma, and death)
Alkalinize the blood

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4
Q

Liver ammonia income

A

Ammonia form from portal blood
Alanine form from Muscles (mostly) and other tissues

Smaller quantities of other amino acids, in addition to glutamine

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5
Q

Kidney ammonia income

what happen in kidney

A

Mostly in form of glutamine from other tissues

Glutaminase release NH3 from glutamine

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6
Q

Intestine ammonia income

A

Intestinal bacteria
Glutamine from dietary protein
Tissue Glutamines

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7
Q

Where does Glutaminase work

A

kidney : irreversible
Kidney glutaminase is induced by chronic acidosis

The liver has only small quantities of glutaminase

Intestine: ammonium ion from deamination can be sent directly to the liver via the portal blood

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8
Q

where does glutamate dehydrogenase work

what is the product

A

Catalyzes the oxidative deamination of glutamate
reversible : make NADH
Produces a-ketoglutarate

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9
Q

where does aminotransferases work

what is the co enzyme

A 
Both muscles and liver: AST just in liver
Pyridoxal phosphate (PLP) derived from vitamin B6 is Coenzyme
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10
Q

Urea in liver produced from which nitrogens

A

Ammonia directly taken from portal blood

Ammonia produced from Glutamate by glutamate dehydrogenase

Aspartate produced from adding an amino group to oxaloacetate (AST)

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11
Q

Most tissues nitrogen destiny

A

Glutamine synthetase
Captures excess nitrogen by aminating glutamate to form glutamine

irreversible
Ammonia become available through deaminations

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12
Q

How does alanine produced in muscles

which enzyme and substrate and coenzyme are involved

A

aminogroup transfer to a ketoglutarate to form glutamate
aminogroup transfer from glutamate to pyruvate to form alanine (ALT)
B6 is co enzyme

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13
Q

what does Urea produced from in mitochondria

A

Carbamoyl phosphate: Produced from ammonium ion and Carbon dioxide: by Mitochondrial carbamoyl phosphate synthetase I

Aspartate added outside mitochondria

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14
Q

what is the coenzyme of carbamoyl phosphate synthetase I

A

N-Acetylglutamate

Obligate activator
Produced only when free amino acids are present

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15
Q

name two Obligate activators of enzymes

A

N-acetylglutamate in carbamoyl phosphate synthetase I

Acetyl coA in pyruvate carboxylase

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16
Q

name the enzymes of intramitochondrial urea cycle and their products

A

Carbamoyl Phosphate Synthetase : carbamoyl phosphate

Ornithine Transcarbamoylase : Citrulline

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17
Q

primary substrate of urea cycle

A

NH4 HCO3 2ATP : carbamoyl phosphate

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18
Q

cytoplasmic steps of urea cycle

A

Citrulline with aspartate and ATP by Argininosuccinate Synthetase to Argininosuccinate

then by Argininosuccinate Lyase to arginine and release fumarate
then by arginase to ornithine and releas urea

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19
Q

what kind of aminoacid is Arginine

A

Essential only in positive nitrogen balance situation like children
it should help in making new histones

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20
Q

Symptoms of defect in the urea cycle

A

combination of hyperammonemia, elevated blood glutamine, and decreased BUN

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21
Q

Symptoms of neonatal onset urea cycle defects

A

Infants typically appear normal for the first 24 hours

During the 24- to 72-hour postnatal period, symptoms of lethargy, vomiting, and hyperventilation begin
if not treated, progress to coma, respiratory failure, and death

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22
Q

Carbamoyl Phosphate Synthetase deficiency symptoms and features

A

↑[NH4+], hyperammonemia
Blood glutamine is increased
BUN is decreased

No orotic aciduria
Autosomal Recessive

Cerebral edema
Lethargy, convulsions, coma, death

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23
Q

Ornithine Transcarbamoylase deficiency symptoms and features

A

↑[NH4+], hyperammonemia
Blood glutamine is increased
BUN is decreased

Orotic aciduria
X-linked recessive

Cerebral edema
Lethargy, convulsions, coma, death

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24
Q

what is the mechanism of orotic aciduria

A

↑carbamoyl phosphate in cytoplasm
Substrate for aspartate transcarbamoylase in pyrimidine Synthesis
↑orotic acids

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25
Q

Treatment of defects in urea cycle

A

Low protein diet
administration of sodium benzoate or phenylpyruvate
provide an alternative route for capturing and excreting excess nitrogen

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26
Q

Phenylketonuria etiology

A

Phenylalanine Hydroxylase Deficiency

Tetrahydrobiopterin ( a coenzyme) Deficiency

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27
Q

PKU symptoms and prevention

A

Infants normal at birth

If untreated show slow development, severe mental retardation, Musty odor in diaper ,autistic symptoms, and loss of motor control

Children may have pale skin and white-blonde hair > Lack of tyrosine > no melanin

routinely screened a few days after birth for blood phenylalanine level

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28
Q

what is the etiology of neurotoxic effects in PKU

A

High levels of phenylalanine

not phenylketones

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29
Q

PKU treatment

A

Life-long semisynthetic diet Low in phenylalanine (small quantities are necessary : essential amino acid) and tyrosine supplements

Aspartame (N-aspartyl-phenylalanine methyl ester), an artificial sweetener, must be avoided

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30
Q

complications in pregnant PKU if not maintain metabolic control

A

mental retardation (less profound than a child with untreated PKU), microcephaly, and low birth weight

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31
Q

Alcaptonuria etiology

A

Homogentisate Oxidase Deficiency

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32
Q

Alcaptonuria symptoms

A

Dark urine
Ochronosis
Arthritis

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33
Q

Albinism etiology

A

Tyrosinase deficiency

no production of melanin

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34
Q

Maple Syrup Urine Disease etiology

A

Branched-Chain Ketoacid Dehydrogenase Deficiency

defect in CoA production

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35
Q

what are coenzymes for Branched-Chain Ketoacid Dehydrogenase and what other enzymes share them

A

thiamine, lipoic acid, CoA, FAD, NAD+

Pyruvate dehydrogenase, a-ketoglutarate dehydrogenase

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36
Q

What are Branched-Chain Ketoacid

A

produced from their cognate amino acids, valine, leucine, and isoleucine through deamination

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37
Q

Maple Syrup Urine Disease symptoms

A

normal for the first few days of life
become progressively lethargic, lose weight, and have alternating episodes of hypertonia and hypotonia, and the urine develops a characteristic odor of maple syrup

Ketosis, coma, and death ensue if not treated

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38
Q

what are propionic acid pathway enzymes deficiency
what substances accumulate in each
what aminoacids are involved

A

Propionyl-CoA Carboxylase Deficiency: Propionic acid, methyl citrate, hydroxypropionic acid

Methylmalonyl-CoA Mutase Deficiency: methylmalonic aciduria

Valine, methionine, isoleucine, and threonine

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39
Q

propionic acid pathway enzymes deficiency symptoms

A

neonatal ketoacidosis

methylmalonic aciduria can be present depending on the enzyme involved

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40
Q

what is co factor of Methylmalonyl-CoA Mutase

A

B12

41
Q

what is co factor of Propionyl-CoA Carboxylase

A

Biotin

42
Q

Homocystinemia/Homocystinuria etiology

A

Cystathionine synthase deficiency

Homocysteine methyltransferase deficiency
Methyltetrahydrofolate deficiency

43
Q

what is co factor of Cystathionine synthase

A

B6

44
Q

what is co factor of Homocysteine methyltransferase

A

Methyl THF

B12

45
Q

How does homocystein produced

A

Methionine with adenosine produce S-adenosylmethionine(methyl donor)
then become S-adenosylhomocysteine
release adenosine and become homocystein

46
Q

what will happen for homocystein

A

by cystathione synthase and B6 become cystathione

by homocysteine methyl transferase and B12 and methyl THF become methionine

47
Q

where would the methyl group from S-adenosylmethionine be used

A

Epinephrine

N-methylguanine cap on mRNA

48
Q

Homocystinemia/Homocystinuria Symptoms & treatment

A

cardiovascular disease, deep vein thrombosis, thromboembolism, and stroke, dislocation of the lens (downward and inward in contrast to marfan) and mental retardation

low in methionine
partial activity of cystathionine synthase respond well to pyridoxine administration

49
Q

which Vitamin deficiencies would produce homocystinemia

A

Folate deficiency
Vitamin B12
Vitamin B6
produce a mild form of homocysteinemia

50
Q

name a single carbon donor

A

tetrahydrofolate (THF)

51
Q

how is THF produced

A

two reductions catalyzed by dihydrofolate reductase

52
Q

where does Methotrexate affect

A

Methotrexate inhibits DHF reductase

53
Q

what is the folate cycle

A

THF take one carbon unit, then gives it to purines and thymidine and become methyl THF
in the presence of B12 and homocysteine methyl transferase it will donate its methyl group and become THF

54
Q

what is the mechanism of B12 deficiency in producing megaloblastic anemia

A

halting the folate cycle in methyl THF will result in loss of active folate

55
Q

causes of folate deficiency

A

Pregnancy (neural tube defects in fetus may result)
Alcoholism
Severe malnutrition

56
Q

causes of B12 deficiency

A 
Pernicious anemia
Gastric resection
Chronic pancreatitis
Severe malnutrition
Vegan
Infection with D. latum
57
Q

features of folate deficiency

A

↑ homocysteine

↓ Methionine

58
Q

features of B12 deficiency

A

↑ homocysteine
↓ Methionine
↑ methylmalonyl aciduria

59
Q

features of B6 deficiency

A

↑ homocysteine

↑ Methionine

60
Q

symptoms of Folate and B12 Deficiency

A

Macrocytic anemia
MCV>100
PMN nucleus more than 5 lobes
Homocystinemia with risk for cardiovascular disease

61
Q

B12 deficiency specific symptoms

A

Methylmalonic aciduria
Progressive peripheral neuropathy

Deficiency develops in years

62
Q

Folate deficiency specific symptoms

A

Deficiency develops in 3-4 months

63
Q

cathecholamine synthesis pathway

A

Tyrosine by tyrosine hydroxylase and tetrahydrobiopterin to 3,4 dihydrophenylalanine (DOPA)
by DOPA decarboxylase and B6 to Dopamine
by Dopamine b-hydroxylase and VitC/Cu2+ to norepinephrine
by phenylethanolamine methyltransferase and s-adenosylmethionine to epinephrine

64
Q

co enzyme for tyrosine hydroxylase

A

tetrahydrobiopterin THB

65
Q

co enzyme for DOPA decarboxylase

A

B6

66
Q

co enzyme for Dopamine b-hydroxylase

A

VitC/Cu2+

67
Q

what is the dopaminergic drug used in parkinson

and why

A

L-dopa can cross BBB

catecholamines cannot enter the brain so brain synthetize them locally

68
Q

where is heme needed

A

hemoglobin myoglobin
cytochromes (electron transport chain, cytochrome P-450, cytochrome b5)
enzymes catalase, peroxidase
soluble guanylate cyclase stimulated by nitric oxide

69
Q

Rate limiting enzyme in heme synthesis in liver

what is its regulator

A

δ-aminolevulinate synthase (ALA)

repressed by heme

70
Q

what is the first step of heme synthesis
what is co factor
what is its regulator

A

Glycine with succinyl coA by ALA synthase and B6 in mitochondria produce δ-aminolevulinic acid
repressed by heme

71
Q

what are the steps in 1st part of heme synthesis

and what disease will happen if it goes wrong

A

ALA by ala dehdratase to prophobilinogen
by porphobilinogen deaminase to hydroxymethylbilane
this step can produce acute intermittent porphyria
by Uroporphyrinogen synthase to uroporphyrinogen

72
Q

what are the steps in 2nd part of heme synthesis

and what disease will happen if it goes wrong

A

Uroporphyrinogen to coproporphyrinogen by Uroporphyrinogen decarboxylase
this step can produce porphyria cutanea tarda
then to protoporphyrin
protoporphyrin by Ferrochelatase to heme with Fe2+

73
Q

which enzyme in heme synthesis can be inhibited by lead

A

ferrochelatase

ALA dehdratase

74
Q

what is uroporphyrinogen significance

A

first porphyrin in heme synthesis

before this substance, enzyme disorder will not result in photosensitivity and cutaneous lesions

75
Q

what are the symptoms of Acute intermittent porphyria

A

late-onset
autosomal dominant, variable expression
Abdominal pain, often resulting in multiple laparoscopies (scars on abdomen)
Anxiety, paranoia, and depression
Paralysis
Motor, Sensory or autonomic neuropathy
Weakness
Excretion of ALA (δ-aminolevulinic) and PBG (porphobilinogen) during episodes
In severe cases, dark port-wine color to urine on standing

76
Q

which enzyme is problematic in Acute intermittent porphyria

what shouldnt be done in these patients

A

porphobilinogen deaminase

never give barbiturates

77
Q

what’s the relationship between barbiturates and porphyria

A

Hydroxylated by the microsomal cytochrome P-4S0 system in the liver
Results in stimulation of cytochrome P-4S0 synthesis
reduces heme levels
lessens the repression of ALA synthase
more porphyrin precursor synthesis
Indirect production of more precursors by the barbiturates exacerbates the disease

78
Q

what to administer in porphyria patients

A

β-Carotene is often administered to porphryia patients with photosensitivity to reduce the production of reactive oxygen species

79
Q

what are the symptoms of Porphyria Cutanea Tarda

A

Most common porphyria
Autosomal dominant, late-onset hepatic porphyria
Photosensitivity
Inflammation, blistering, shearing of skin in areas exposed to light
Hyperpigmentation
Hepatotoxic substances, such as excessive alcohol or iron deposits, can exacerbate it
red-wine urine if it is allowed to stand

80
Q

which enzyme is problematic in Porphyria Cutanea Tarda

what shouldnt be done in these patients

A

Uroporphyrinogen decarboxylase

avoiding alcohol

81
Q

what is the result of Vitamin B6 deficiency in heme pathway

what will cause in its deficiency

A

ALA synthase, the rate-limiting enzyme, requires pyridoxine (vitamin B6)
Associated with isoniazid therapy for tuberculosis
may cause sideroblastic anemia with ringed sideroblasts
Ring sideroblasts is accumulation of Iron in the mitochondria of cell

82
Q

what is the mechanism of Iron deficiency

A

The last enzyme in the pathway, heme synthase (ferrochelatase), introduces the Fe2+ into the heme ring
Deficiency of iron produces a microcytic hypochromic anemia

83
Q

which enzymes are involved in lead Poisoning

what is its result and symptoms

A

Lead inactivates many enzymes including ALA dehydrase and ferrochelatase
microcytic sideroblastic anemia with ringed sideroblast
Coarse basophilic stippling of erythrocytes
Headache, nausea, memory loss
Abdominal pain, diarrhea (lead colic)
Lead lines in gums
Lead deposits in abdomen and epiphyses of bone seen on radiograph
Neuropathy (claw hand, wrist-drop)
Increased urinary ALA
Increased free erythrocyte protoporphyrin

84
Q

What is the result of ferrochelatase failure

how can we diagnose it

A

Nonenzymatic insertion of Zn2+ to form zinc protoporphyrin

This complex is extremely fluorescent and is easily detected

85
Q

what are the etiologies of lead poisoning

how can it get diagnosed

A

Lead paint, Pottery glaze, Batteries

Diagnose by measuring blood lead level

86
Q

what is the etiology of red wine urine in porphyria

A

porphyrin”ogen”s are colourless
In the presence of oxygen, they spontaneously oxidize, formirng a conjugated double-bond network in the compounds named porphyr”in” which is colourfoul

87
Q

what forms of iron we eat, we absorb

binds to transferrin, ferritin, use in heme

A

we eat Fe3+, absorb Fe2+
ferritin and transferrin Fe3+
heme Fe 2+

88
Q

How is iron bind transferrin and ferritin

A

Feroxidase(ceruloplasmin, Cu2+ protein) oxidize Fe2+ to bind with transferrin
Ferritin oxidizes Fe2+ itself

89
Q

What is Hemosiderin

A

ferritin precipitation

Hemosiderin binds excess Fe3+ to prevent escape of free Fe3+ into the blood, where is toxic

90
Q

what is daily need and rate of absorption of iron

A

Human absorb 1mg/d Iron, 10% of Iron intake will be absorbed > daily need 10mg

91
Q

what is Hemochromatosis

Prevalence, genetic, symptoms

A

Autosomal recessive disease, defect in HFE channel
prevalence of 1/200, men >40 years old and in older women
daily intestinal absorption of 2-3 mg of iron
Over 20-30 years
Early symptoms of early fatigability and lethargy
Hemosiderin deposits are found in the liver (cirrhosis), pancreas (Diabetes), skin, and joints (Arthritis)

92
Q

bilirubin metabolism untill secretion

A

globin degrade to its aminoacids
Heme to Iron and Carbon monoxide and biliverdin
bilirubin in blood with albumin
Hepatocytes conjugate it with 2 glucuronic acid
secreted into the bile

93
Q

Conjugation enzyme of bilirubin and its substrate and reslults

A

UDP glucuronyl transferase
add 2 UDP glucuronate to bilirubin
make bilirubin diglucuronide

94
Q

bilirubin secretion features

A

Intestinal bacteria cut off both sugars
glycolysis then NADH
Electrons then put on bilirubin and make urobilinogen
mostly in feces in form of stercobilin
small absorb and in urine in form of urobilin

95
Q

what is the color of heme, biliverdin, bilirubin

A

Purple, Green, Yellow-Orange

96
Q

what is the color of urine in hemolysis

A

deeper colored due to excessive bilirubin production and urobilinogen in intestine
so it is also increased in urine

97
Q

etiology of jaundice in newborns

therapy

A

Massive erythrocyte destruction in 1st days, HbF not respond to 2,3 BPG
UDP-glucuronyl transferase induced only at birth

Phototherapy > Blue light(not UV), Bil absorb light, fragments to water soluble particles

98
Q

Lab results in alcoholic liver

A

AST increases more than ALT

03 Biochemistry (5 decks)

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