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03 Biochemistry > 17 Aminoacid Metabolism > Flashcards

17 Aminoacid Metabolism Flashcards

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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
Treatment of defects in urea cycle
Low protein diet administration of sodium benzoate or phenylpyruvate provide an alternative route for capturing and excreting excess nitrogen
26
Phenylketonuria etiology
Phenylalanine Hydroxylase Deficiency Tetrahydrobiopterin ( a coenzyme) Deficiency
27
PKU symptoms and prevention
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
28
what is the etiology of neurotoxic effects in PKU
High levels of phenylalanine | not phenylketones
29
PKU treatment
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
30
complications in pregnant PKU if not maintain metabolic control
mental retardation (less profound than a child with untreated PKU), microcephaly, and low birth weight
31
Alcaptonuria etiology
Homogentisate Oxidase Deficiency
32
Alcaptonuria symptoms
Dark urine Ochronosis Arthritis
33
Albinism etiology
Tyrosinase deficiency | no production of melanin
34
Maple Syrup Urine Disease etiology
Branched-Chain Ketoacid Dehydrogenase Deficiency | defect in CoA production
35
what are coenzymes for Branched-Chain Ketoacid Dehydrogenase and what other enzymes share them
thiamine, lipoic acid, CoA, FAD, NAD+ Pyruvate dehydrogenase, a-ketoglutarate dehydrogenase
36
What are Branched-Chain Ketoacid
produced from their cognate amino acids, valine, leucine, and isoleucine through deamination
37
Maple Syrup Urine Disease symptoms
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
38
what are propionic acid pathway enzymes deficiency what substances accumulate in each what aminoacids are involved
Propionyl-CoA Carboxylase Deficiency: Propionic acid, methyl citrate, hydroxypropionic acid Methylmalonyl-CoA Mutase Deficiency: methylmalonic aciduria Valine, methionine, isoleucine, and threonine
39
propionic acid pathway enzymes deficiency symptoms
neonatal ketoacidosis | methylmalonic aciduria can be present depending on the enzyme involved
40
what is co factor of Methylmalonyl-CoA Mutase
B12
41
what is co factor of Propionyl-CoA Carboxylase
Biotin
42
Homocystinemia/Homocystinuria etiology
Cystathionine synthase deficiency Homocysteine methyltransferase deficiency Methyltetrahydrofolate deficiency
43
what is co factor of Cystathionine synthase
B6
44
what is co factor of Homocysteine methyltransferase
Methyl THF | B12
45
How does homocystein produced
Methionine with adenosine produce S-adenosylmethionine(methyl donor) then become S-adenosylhomocysteine release adenosine and become homocystein
46
what will happen for homocystein
by cystathione synthase and B6 become cystathione | by homocysteine methyl transferase and B12 and methyl THF become methionine
47
where would the methyl group from S-adenosylmethionine be used
Epinephrine | N-methylguanine cap on mRNA
48
Homocystinemia/Homocystinuria Symptoms & treatment
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
which Vitamin deficiencies would produce homocystinemia
Folate deficiency Vitamin B12 Vitamin B6 produce a mild form of homocysteinemia
50
name a single carbon donor
tetrahydrofolate (THF)
51
how is THF produced
two reductions catalyzed by dihydrofolate reductase
52
where does Methotrexate affect
Methotrexate inhibits DHF reductase
53
what is the folate cycle
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
what is the mechanism of B12 deficiency in producing megaloblastic anemia
halting the folate cycle in methyl THF will result in loss of active folate
55
causes of folate deficiency
Pregnancy (neural tube defects in fetus may result) Alcoholism Severe malnutrition
56
causes of B12 deficiency
``` Pernicious anemia Gastric resection Chronic pancreatitis Severe malnutrition Vegan Infection with D. latum ```
57
features of folate deficiency
↑ homocysteine | ↓ Methionine
58
features of B12 deficiency
↑ homocysteine ↓ Methionine ↑ methylmalonyl aciduria
59
features of B6 deficiency
↑ homocysteine | ↑ Methionine
60
symptoms of Folate and B12 Deficiency
Macrocytic anemia MCV>100 PMN nucleus more than 5 lobes Homocystinemia with risk for cardiovascular disease
61
B12 deficiency specific symptoms
Methylmalonic aciduria Progressive peripheral neuropathy Deficiency develops in years
62
Folate deficiency specific symptoms
Deficiency develops in 3-4 months
63
cathecholamine synthesis pathway
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
co enzyme for tyrosine hydroxylase
tetrahydrobiopterin THB
65
co enzyme for DOPA decarboxylase
B6
66
co enzyme for Dopamine b-hydroxylase
VitC/Cu2+
67
what is the dopaminergic drug used in parkinson | and why
L-dopa can cross BBB | catecholamines cannot enter the brain so brain synthetize them locally
68
where is heme needed
hemoglobin myoglobin cytochromes (electron transport chain, cytochrome P-450, cytochrome b5) enzymes catalase, peroxidase soluble guanylate cyclase stimulated by nitric oxide
69
Rate limiting enzyme in heme synthesis in liver | what is its regulator
δ-aminolevulinate synthase (ALA) | repressed by heme
70
what is the first step of heme synthesis what is co factor what is its regulator
Glycine with succinyl coA by ALA synthase and B6 in mitochondria produce δ-aminolevulinic acid repressed by heme
71
what are the steps in 1st part of heme synthesis | and what disease will happen if it goes wrong
ALA by ala dehdratase to prophobilinogen by porphobilinogen deaminase to hydroxymethylbilane this step can produce acute intermittent porphyria by Uroporphyrinogen synthase to uroporphyrinogen
72
what are the steps in 2nd part of heme synthesis | and what disease will happen if it goes wrong
Uroporphyrinogen to coproporphyrinogen by Uroporphyrinogen decarboxylase this step can produce porphyria cutanea tarda then to protoporphyrin protoporphyrin by Ferrochelatase to heme with Fe2+
73
which enzyme in heme synthesis can be inhibited by lead
ferrochelatase | ALA dehdratase
74
what is uroporphyrinogen significance
first porphyrin in heme synthesis | before this substance, enzyme disorder will not result in photosensitivity and cutaneous lesions
75
what are the symptoms of Acute intermittent porphyria
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
which enzyme is problematic in Acute intermittent porphyria | what shouldnt be done in these patients
porphobilinogen deaminase | never give barbiturates
77
what's the relationship between barbiturates and porphyria
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
what to administer in porphyria patients
β-Carotene is often administered to porphryia patients with photosensitivity to reduce the production of reactive oxygen species
79
what are the symptoms of Porphyria Cutanea Tarda
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
which enzyme is problematic in Porphyria Cutanea Tarda | what shouldnt be done in these patients
Uroporphyrinogen decarboxylase | avoiding alcohol
81
what is the result of Vitamin B6 deficiency in heme pathway | what will cause in its deficiency
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
what is the mechanism of Iron deficiency
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
which enzymes are involved in lead Poisoning | what is its result and symptoms
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
What is the result of ferrochelatase failure | how can we diagnose it
Nonenzymatic insertion of Zn2+ to form zinc protoporphyrin | This complex is extremely fluorescent and is easily detected
85
what are the etiologies of lead poisoning | how can it get diagnosed
Lead paint, Pottery glaze, Batteries | Diagnose by measuring blood lead level
86
what is the etiology of red wine urine in porphyria
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
what forms of iron we eat, we absorb | binds to transferrin, ferritin, use in heme
we eat Fe3+, absorb Fe2+ ferritin and transferrin Fe3+ heme Fe 2+
88
How is iron bind transferrin and ferritin
Feroxidase(ceruloplasmin, Cu2+ protein) oxidize Fe2+ to bind with transferrin Ferritin oxidizes Fe2+ itself
89
What is Hemosiderin
ferritin precipitation | Hemosiderin binds excess Fe3+ to prevent escape of free Fe3+ into the blood, where is toxic
90
what is daily need and rate of absorption of iron
Human absorb 1mg/d Iron, 10% of Iron intake will be absorbed > daily need 10mg
91
what is Hemochromatosis | Prevalence, genetic, symptoms
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
bilirubin metabolism untill secretion
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
Conjugation enzyme of bilirubin and its substrate and reslults
UDP glucuronyl transferase add 2 UDP glucuronate to bilirubin make bilirubin diglucuronide
94
bilirubin secretion features
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
what is the color of heme, biliverdin, bilirubin
Purple, Green, Yellow-Orange
96
what is the color of urine in hemolysis
deeper colored due to excessive bilirubin production and urobilinogen in intestine so it is also increased in urine
97
etiology of jaundice in newborns | therapy
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
Lab results in alcoholic liver
AST increases more than ALT

03 Biochemistry (5 decks)

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