Biochem Flashcards
Enzymes of glycolytic enzyme deficiency
Aldolase A, enolase, phosphofructokinase, pyruvate kinase
What do red cells require for energy production?
Anaerobic glycolysis
In which metabolic process is pyruvate carboxylase seen?
One of the gluconeogenetic pathway enzymes in mitochondria
Catalyzes the conversion of pyruvate to oxaloacetatew
Clinical manifestation of pyruvate carboxylase deficiency
Lactic acidosis and fasting hypoglycemia
What is primase?
RNA polymerase
Where is the starting point of DNA polymerase in the RNA primer as a starting point for synthesis?
In the 3’ hydroxyl group of the RNA primer
Crucial enzyme for bacterial replication as DNA polymerase
Primase
Primary enzyme responsible for synthesis of daughter DNA strands
DNA polymerase III
Functions chiefly to replace the RNA primers with DNA segments
DNA polymerase I
Where does heme synthesis is done?
Partly in the mitochondria and partly in the cytoplasm
When the erythrocyte mature and looses the mitochondria, which ability is lost?
The ability to generate heme and there hemoglobin
Which heme synthesis substrates are seen in mitochondria of erythrocyte precursors?
Protoporphyrinogen IX
Protoporphyrin IX
Heme
What type of disorder is orotic aciduria?
Pyrimidine metabolism
What characterizes orotic aciduria?
Hypochromic megaloblastic anemia, neurologic abnormalities, growth retardation and excretion of high amounts of orotic acid in the urine
First substrates for pyrimidine synthesis
ATP, CO2 and gluthamine
Which enzyme is required to form carbamoyl phosphate in pyrimidine synthesis?
Carbamoyl phosphate synthase II
Regulatory step for pyrimidine synthesis
Carbamoyl phosphate
Which are the defective enzymes in orotic aciduria?
Orotate phosphoribosyl transferase and OMP decarboxylase
What is the final product of pyrimidine synthesis?
Orotate to uridine 5’ monophosohate (UMP)
What needs to be supplemented in Orotic aciduria?
Uridine
When is indicated pyridoxine supplementation?
During treatment with isoniazid
Required for hydroxylation of proline and lysine residues in collagen synthesis
Ascorbic acid (vitamin C)
How does uridine supplementation improves symptoms of orotic aciduria?
By inhibiting carbamoyl phosphate synthase II
What is the product of phenylalanine hydroxylase?
Tyrosine
What is deficient in homozygous phenylketonuria patients?
Phenylalanine hydroxylase
Which enzyme is inhibited by the excess of phenylalanine? What is its function?
Tyrosinase, enzyme responsible for the synthesis of melanin from tyrosine
When do PKU patients develop mental retardation and the other clinical findings?
By 6th months
What is the treatment for Hartnup disease?
Nicotinic acid or nicotinamide and a high protein diet
Which vitamin may be deficient in case of Hartnup disease?
Niacin
What causes niacin deficiency in Hartnup disease?
Loss of dietary tryptophan
What could cause loss of tryptophan in Hartnup disease?
Defective intestinal and renal tubular absorption
After how much time of starvation does the body start using lipids instead of glucose?
After 16-24 hours
Which enzyme deficiency leads to impaired beta oxidation?
Acyl CoA dehydrogenase
Who causes Von Gierke disease?
Deficiency of glucose 6 phosphatase
Clinical manifestations of glucose 6 phosphatase enzyme
Hypoglycemia, stunted growth, lactic acidosis and hypertriglyceridemia
Enzyme that catalyzes the first step in fatty acid synthesis
Acetyl CoA carboxylase
What is the result of splice site mutations?
Result in the production of larger proteins with altered function but preserved immune reactivity
Why is lipoic acid for pyruvate dehydrogenase?
Because it is involved in the decarboxylation of alpha ketoacids and the transfer of alkyl groups
The transfer of alkyl group from pyruvate to coenzyme A is essential for the function of pyruvate dehydrogenase
Which enzymes do PDH require?
CoA, FAD, lipoic acid, NAD and thiamine pyrophosphate
What is the result of decreased functioning of pyruvate dehydrogenase?
Increased conversion of pyruvate to lactate
Why does pyruvate becomes lactate in absence of the coenzymes?
By the enzyme lactate dehydrogenase in an effort to regenerate NAD+, and this will eventually lead to lactic acidosis
In which pathways does lipoic acid works?
TCA cycle
Alpha ketoglutarate dehydrogenase
Branched chain ketoacid dehydrogenase
Which type of disorder is citrullinemia?
Urea cycle that results from deficiency of argininosuccinate synthase
Cofactor needed for argininosuccinate synthase
ATP
Which deficiency is seen in methyl alonic aciduria?
Vitamin B12 dependent enzyme methylmalonate mutase
Results from a deficiency in cystathione synthase
Homocystinuria
What characterizes homocystinuria?
Premature atherosclerosis
how is homocysteine by the body?
Conversion to cysteine by combined actions of two vitamin B6 requiring enzymes
Conversion to methionine by folate and vitamin B 12 dependent process
Which enzymes in homocysteine require vitamin B6?
Cystathionine synthase and cystathionase
Pathology associated to pyrimidine synthesis
Orotic aciduria
Which enzyme is deficient in orotic aciduria?
Orotate phosphoribosyl transferase
Which coenzyme does Orotate phosphoribosyl transferase require?
Glutathione
Glycogen storage disease type V
McArdle disease
Which enzyme is deficient in McArdle disease?
Myophosphorylase
Deficiency of this enzyme leads to decreased breakdown of glycogen during exercise, resulting in poor exercise tolerance, muscle cramps and rhabdomyolysis
Myophosphorylase
This pathway maintains cellular NADPH levels and produces oentose sugars for nucleotide synthesis
Pentose phosphate pathway (hexose monophosphate pathway)
What happens in Pentose phosphate pathway (hexose monophosphate pathway) ?
Conversion of glucose 6 phosphate to 6 phosphogluconate by glucose 6 phosphate
This rRNA molecule is essential for initiation of protein synthesis in prokaryotes
16S rRNA
Where is 16S rRNA found?
In the prokaryotic 30S ribosomal subunit
What is the function of 16S rRNA subunit?
Expresses a sequence complementary to Shine Dalgarno sequence in all prokaryotic mRNA
These two complementary sequences allow the mRNA and the 30S ribosomal subunit to bind in preparatio. For protein trnalation
16S rRNA and Shine Dalgarno
How is the protein synthesis made, after binding of 30S ribosomal subunit is bound to mRNA?
An initiator tRNA binds to the AUG codon, the 50S ribosomal subunit joins the complex and protein synthesis begins
Where is 23S rRNA is found?
In the 50S ribosomal subunit
What is 23S rRNA? And what is its function?
Its a peptidyltransferase, who facilitates peotide bond formation in protein translation
Process by which the ribosome advances to the next mRNA codon
Translocation
It recognizes and binds the mRNA codon and assures placement of the proper amino acid in the growing polypeptide chain
Anticodon
Of the tRNA which is the site of amino acid attachment?
3’
What composes 5’ end of tRNA?
Of terminal guanosine
Responsible for transporting amino acids to the site of protein synthesis and introducing them into the growing polypeptide chain at the correct locations
tRNA
What is the function of the anticodon?
Recognizes a specific codon on the mRNA molecule
Who brakes down glycogen?
Glycogen phosphorylase
Who phosphorylates (activates) glycogen phosphorylase?
Phosphorylase kinase
Who dephosphorylates (inactivates) glycogen phosphorylase?
Phosphoprotein phosphatase
Main organs where glycogen works
Liver and muscle
In the liver how is Phosphorylase kinase activated?
Through the binding of epinephrine and glucagon to Gs protein coupled receptors, which increases cAMP concentrations
In the muscle how is Phosphorylase kinase activated?
Increased intracellular calcium and epinephrine
Factors that inhibit phosphorylated glycogen phosphorylase
By ATP and glucose 6 phosphate in both liver and muscle cells
Process where astrocytes and neurons interact to regulate the metabolism of glutamate, glutamine and ammonia
Glutamate glutamine cycle
Which is the metabolic process of glutamine in the brain?
Glutamine is released by astrocytes and taken up by neuron, where it is either converted to glutamate for use as a neurotransmitter or transaminated into alpha ketoglutarate for use in krebs cycle
Which enzyme detoxifies ammonia to glutamine?
Glutamate dehydrogenase
What is the final effect of Glutamate dehydrogenase on the brain?
Detoxifies ammonia to glutamine, depleting alpha ketoglutarate and further impairing energy metabolism in the brain
Responsible for transport of fatty acids into the mitochondria for beta oxidation
Carnitine
When does impaired beta oxidation of fatty acids to acetyl CoA occur?
With excessive alcohol consumption
Who metabolizes lactate?
Liver
Tryptophan derivative formed by bacteria in the gut and normally cleared by the liver
Oxindole
When do we see elevated levels of oxindole?
In patients with hepatic encephalopathy
What is the result of hyperammonemia in hepatic encephalopathy?
Depletion of alpha ketoglutarate, causing inhibition of Krebs cylce
Depletes glutamate and causes accumulation of glutamine, resulting in astrocyte swelling and dysfunction
Glutamate excitatory or inhibitory neurotransmitter?
Excitatory
Allosteric activator of pyruvate carboxylase
Acetyl CoA
Who allosterically inhibits pyruvate kinase?
Alanine
When are methylmalonilic acid levels increased?
With vitamin B12 deficiency
Hallmark of erythropoietin protoporphyria
Increased erythrocyte protoporphyrin
Essential in de novo pathway for dTMP production because regulates the supply of four nucleotide precursors of DNA replication
Thymidylate synthase
Percentage pf thymidine kinase that normally accounts for dTMP synthesis
5-10%
What is elevated in folate deficiency?
Homocysteine
Major source of nitrogen in the synthesis of nucleotides
Glutamine
Contributes a nitrogen atom to the biosynthesis of dUMP
Glutamine
In case of folate synthesis, what is not formed?
Deoxythymidine monophosphate (dTMP)
What is the result of folate deficiency inhibiting the formation of Deoxythymidine monophosphate (dTMP)?
Limits DNA synthesis and promotes megaloblastosis and erythroid precursor cell apoptosis
Which antibodies confirm the diagnosis of rheumatoid arthritis?
Anti cyclic citrullinated peptide (anti CCP)
What is the citrullation?
Tissue inflammation causes arginine residues in proteins such as vimentin to be enzymatically converted into citrulline
What does antiphospholipid antibody causes?
Hypercoagulability, paradoxical partial thromboplastin time (PTT) prolongation, and recurrent miscarriages
What could be the result of homozygous mutation of glucokinase in pregnant women?
Fetal growth retardation and hyperglycemia at birth
What is the importance of PI3K/Akt/mTOR pathway?
Is an intracellular signaling pathway important for anti apoptosis, cellular proliferation and angiogenesis
Which factors enhance the activity of PI3K/Akt/mTOR pathway contributing with cancer pathogenesis?
Growth factor receptors, Akt, mTOR, or PTEN
A disease caused by tissue deposition of monosodium urate crystals
Gout
Which is a known risk factor for gout?
Elevated uric acid levels
Which is a possible cause of hyperuricemia?
Increased purine metabolism
Its the enzyme responsible for the production of the activated ribose necessary for de novo synthesis of purity and pyrimidines Nucleotides
Phosphoribosyl pyrophosphate (PRPP)
What could be the result of more purine molecules undergoing degradation?
Hyperuricemia and an increased risk of gout
Disease caused by glucose 6 phosphate deficiency
Von Gierke disease
Disease caused by acid maltase deficiency
Pompe disease
In which patients does gout occur more frequently?
In patients with activating mutation involving phosphoribosyl pyrophosphate synthase due to increased production and degradation of purines
What is mainly affected in acute gouty arthritis?
First metatarsophalangeal joint or knee
Swelling, erythema and exquisite tenderness
Symptoms develop rapidly over 24 hours
How is the diagnosis made in Acute gouty arthritis?
Joint aspiration shows needle shapped, negatively birefringent crystals
Treatment for acute gouty arthritis
NSAIDs (eg naproxen, indomethacin) preferred if no contraindications
Colchicine used as a second line therapy
Which are the primary cells responsible for intense inflammatory response seen in patients with gout?
Neutrophils
Which is the function of Colchicine?
Impairs neutrophil migration and phagocytosis by interfering with microtubule formation
Another function of this drug is to decrease tyrosine phosphorylation in in response to monosodium urate crystals
Colchicine
Which drug inhibits mast sell degranulation?
Cromolyn sodium
Which cell functions require Ubiquitination?
Antigen processing Muscle wasting Cell cycle regulation DNA repair Disposal of misfolded proteins and regulatory enzymes
Which system impairment can contribute to the development of neurodegenerative disorders such as Parkinson disease and Alzheimer?
Ubiquitin-proteasome system
Which genes promote the degradation of misfolded proteins via the ubiquitin proteasome system?
Parkin
PINK1
DJ-1
Which genes are mutated in cases of autosomal recessive forms of Parkinson’s disease?
Parkin
PINK1
DJ-1
Autosomal recessive forms of Parkinson’s disease at what age do they generally manifest?
Less than 50 years
What promotes the formation of euchromatin?
Histone acetylation
What is critical for the functioning of clotting factors II, VII, IX, X and the anticoagulative proteins C and S
Vitamin K dependent gamma carboxylation
Which enzymatic process is inhibited by Warfarin?
Gamma carboxylation
Three key steps for hepatic processing of Bilirubin
Carrier mediated passive uptake of bilirubin at sinusoidal membrane
Conjugation of bilirubin with glucuronic acid
Active biliary excretion of the water soluble nontoxic bilirubin glucoronides
Where is conjugation of bilirubin with glucuronic acid done?
In the endoplasmic reticulum
What is the importance of ubiquitin that undergoes ATP dependent attachment to other proteins?
Labeling them for degradation
What is formed from one molecule of glucose in HMO shunt?
A five carbon sugar, two molecules of NADPH and CO2
Types of reaction of HMP shunt
Oxidative (irreversible) Non oxidative (reversible)
Where do all reactions of HMP shunt occur?
All reaction occur exclusively in the cytoplasm
Primary enzymes involved in the non oxidative step of the HMP shunt
Transaldolase and transketolase
What is the function of transketolase in HMP shunt?
Transfers two carbon groups between substrates of the HMP shunt
When the transketolase transfers two carbon groups between substrates of the HMP shunt, what does it require?
Thiamine pyrophosphate
What does transaldolase transfer in the HMP shunt?
Three carbon groups between substrates of HMP shunt
What is synthesized from glycolysis intermediates fructose 6 phosphate and glyceraldehyde 3 phosphate with help of transketolase and transaldolase?
Ribose from all cells
Where are HMP shunt oxidative reactions active?
In the liver, adrenal cortex, gonads , adipose tissue and erythrocytes
In which metabolic pathways does enolase work?
Glycolysis
What reaction is catalyzed by enolase?
Catalyzes the conversion of 2 phosphoglycerate to phosphoenolpyruvate
Which enzyme catalizes the isomerization of citrate to isocitrate?
Aconitase in TCA cycle
Which are two major functions in the metabolism of glucose through the hexose monophosphate shunt?
Production of NADPH as reducing equivalent
Synthesis of ribose 5 phosphate for nucleotide synthesis
In the oxidative portion of HMP shunt what is the first step?
Glucose 6 phosphate Is first converted to 6 phosphogluconolactone producing one molecule of NADPH
Which enzyme catalizes Glucose 6 phosphate convertion to 6 phosphogluconolactone?
Glucose 6 phosphate dehydrogenase
Which is the rate limiting enzyme for oxidative HMP shunt?
Glucose 6 phosphate dehydrogenase
What is the primary designed for non oxidative reaction of the HMP shunt?
To generate ribose 5 phosphate from intermediates of glycolysis
Which reaction do erythrocytes use to generate large amounts of NADPH?
HMP shunt
What is the purpose of erythrocytes to generate large amounts of NADPH?
To maintain glutathione in a reduced state by the action of gluthatione reductase
Which is the importance to maintain reduce glutathione in erythrocytes?
For protection from oxidative damage resulting from oxidant drugs and oxidizing environmental toxins
Which is the only major pathway for erythrocytes to generate NADPH?
HMP shunt
What is the result of oxidative damage caused to red cells?
Denatured hemoglobin to form insoluble Heinz bodies resulting in erythrocyte destruction in the spleen
X linked disorder that results in episodes of hemolysis during oxidative and infective stress
Glucose 6 phosphate dehydrogenase deficiency
Which enzyme is deficient in glycogen storage type 1?
Glucose 6 phosphate
Which is the biological active form of pantothenic acid?
Coenzyme A
In which pathway is pantothenic acid associated?
TCA because it requires coenzyme A
How does pantothenic acid becomes coenzyme A?
First actively transported into the cell and then undergoes ATP dependent phosphorylation
What is required for the production of mRNA from DNA?
RNA polymerase II
Which is the most common seen in cystic fibrosis?
Codon deletion of the phenylalanine at position 508 in the CFTR protein
Frameshift mutation
Which are the 2 major processes that mantain plasma glucose between meals?
Glycogenolysis and gluconeogenesis
Glycogenolysis
Which is the primary source of glucose for the first 12-18 hours of fasting?
Which is the major process used by the body to keep blood glucose levels within the normal range, once hepatic glycogen storage is depleted?
Gluconeogenesis
During gluconeogenesis, glucose is formed by…
Lactate, glycerol, and glucogenic aminoacids
Can ketone bodies be used to generate glucose?
No
What is the result of acetoacetyl CoA to 3 hydroxy 3 methylglutaryl CoA?
Synthesis of cholesterol and ketone bodies
First fatty acid produced from acetyl CoA during lipogenesis in the fed state
Palmitic acid
How are fatty acids affected during prolonged periods of starvation?
Lipolysis predominates and leads to generation of glycerol and fatty acids
In which process does conversion of fructose 6 phosphate to fructose 1,6 biphosphate occur?
During glycolysis
Who catalizes the conversion of fructose 6 phosphate to fructose 1,6 biphosphate?
Phosphofructokinase
Which is the first step of glycogenolysis?
Breakage of 1,4 glycolysis linkage to form glucose 1 phosphate
Which type of hyperlipoproteinemia is dysbetalipoproteinemia?
Type III
Which are the primary defects in familial dysbetalipoproteinemia?
ApoE3 and ApoE4
Where do we find ApoE3 and ApoE4?
Found on chylomicrons and VLDL that are responsible for binding hepatic apolipoprotein Receptors
What happens if there are not ApoE3 and ApoE4?
The liver cannot efficiently remove chylomicrons and VLDL remnants from the circulation, causing their accumulation in the serum and resultant elevations in cholesterol and triglycerides levels
What composes mainly chylomicrons?
Triacylglycerol
What mainly composes chylomicrons?
Triacylglycerol
Where are chylomicrons synthesized?
On the RER and Golgi apparatus of small intestine enterocytes
What do chylomicrons have once released from enterocytes?
With only ApoB 48 apolipoprotein
What do chylomicrons receive from HDL?
ApoC II and ApoE
Where is Apo 100 present?
On LDL
Who activates lipoprotein lipase?
ApoC II
Who carries ApoC II?
Chylomicrons and VLDL
What is the result of ApoC II deficiency?
Hyperchylomicronemia
Type of hyperlipoproteinemia cuased by ApoC II deficiency
Type 1
Required for esterification of free cholesterol in HDL particles by lecithin- cholesterol acyltransferase (LCAT)
ApoA I
What is the result of ApoA I and LCAT deficiency?
Low HDL and increased circulating free cholesterol levels
Main function of ApoA I
LCAT activation (cholesterol esterification)
Main function of ApoB 48
Chylomicron assembly and secretionby the intestine
Main function of ApoB 100
LDL particle uptake by extrahepatic cells
Main function of ApoC II
Lipoprotein lipase activation
Main function of ApoE 3 and 4
VLDL and chylomicron remnant uptake by the liver cells
How many aminoacids are used in protein synthesis?
20
Which codons correspond to do amino acid Glicyne?
GGU, GGC, GGA and GGG
Many can tRNA anticodons can bind to a few different codons coding for the same aminoacids
Wobble phenomenon
Meneaning thar there are more codons (61) than aminoacids(20)
Genetic code “degenerate”
For what is each tRNA molecule specific for?
For a given aminoacid
What does glucose induced decreased adenylate cyclase activity lead to?
Low intracellular concentrations of cAMP
What causes poor binding of catabolite activator protein to the CAP-DNA binding domain?
Low cAMP levels
What is the result of poor binding of catabolite activator protein to the CAP-DNA binding domain?
Decreased expression of the structural genes of the lac operon
A form of galactosemia that causes a benign disorder characterized by cataracts without hepatocellular manifestations
Galactokinase deficiency
What is deficient in classic galactosemia?
Galactose 1 phosphate uridyl transferase (GALT) deficiency
Which is the most common form of Galactosemia?
Galactose 1 phosphate uridyl transferase (GALT) deficiency
Classic galactosemia
Clinical manifestations of Galactose 1 phosphate uridyl transferase (GALT) deficiency
Vomiting, lethargy and failure to thrive soon after feeding begun
When do Galactose 1 phosphate uridyl transferase (GALT) deficiency manifest?
After initiation of breast-feeding
What is the result of deficiency of galactokynase?
Elevation of galactose levels
What happens to excess circulating galactose?
Is converted to galactitol by aldolase reductase and to galactonic acid by galactose oxidase
What happens to increased levels of galactonic acid and galactitol?
Galactonic acid can be metabolized by HMP shunt, galactitol accumulates in cells
Who is responsible for the formation of cataracts in patients with galactokinase deficiency?
Excess Galactitol
Which enzyme catabolizes the conversion of galactose to galactitol?
Aldolase reductase
This enzyme deficiency results in hereditary fructose intoleranse
Aldolase B
When do patients with aldolase B deficiency become symptomatic?
After ingestion of sucrose and fructose containing food for the first time, typically during infancy
Which enzyme converts glucose 6 phosphate to glucose?
Glucose 6 phosphatase
Last step in production of glucose from gluconeogenesis and glycogenolysis
Conversion of glucose 6 phosphate to glucose by Glucose 6 phosphatase action
Disease caused by Glucose 6 phosphatase deficiency
Glycogen storage disease type 1, von Gierke’s disease
Clinical manifestations of von Gierke’s disease
Hypoglycemia, lactic acidosis and hypertriglyceridemia
How are porphyria classified?
Hepatic or erythropoietic
What is the purpose of Heme synthesized in the liver?
For use in the cytochrome p450 enzyme system
Purpose of heme in the bone marrow
Is generated for hemoglobin use
From what does porphyria manifest?
From accumulation of precursor of porphyrins in the blood, tissues and urine
Drugs that may precipitate acute attacks of intermittent hepatic porphyria
Phenobarbital, griseofulvin, and phenytoin
What else can induce an acute attack of porphyria?
Alcohol and a low caloric diet
How do drugs, alcohol and low caloric diet may precipitate porphyria symptoms?
By decreasing the hepatic concentration of heme
What is the consequence of decreasing the hepatic concentration of heme?
Causes an increase in Hepatic ALA synthase activity
What is the result of increased Hepatic ALA synthase activity?
Leads to increased formation of delta aminolevulinic acid and porphobillinogen
So… What is the result of reduction in heme synthesis?
Leads to increased formation of delta aminolevulinic acid and porphobillinogen
How is the diagnosis of acute intermittent porphyria done?
By demonstrating elevated delta aminolevulinic acid and porphobillinogen during acute attacks
Who inhibits ALA dehydratase and ferrochelatase?
By lead
What is the result of decreased in glucuronyl transferase?
Results in unconjugated hyperbilirubinemia
What is the effect of heme to ALA synthase?
Inhibits it
Highly conserved DNA sequence, usually about 180 nucleotides n lenght
A homebox
What is the function of homebox?
Typically Code for DNA binding transcription factors which alter the expression of genes involved in morphogenesis
What happens to pyruvate when inadequate of our presented in tissues?
Pyruvate is converted to lactate by the enzyme lactate dehydrogenase
What is the purpose to generate lactate?
To generate the NAD+ from NADH+
What are the results of increased lactate levels?
Metabolic acidosis, and will attempt to compensate by causing a respiratory alkalosis
In the presence of oxygen, what does pyruvate preferentially becomes?
Converted to acetyl coenzyme A
Who converts pyruvate to acetyl coenzyme A?
Pyruvate dehydrogenase
Which is the final step of glycolysis?
Is the conversion of phosphoenolpyruvate to pyruvate
Who converts phosphoenolpyruvate to pyruvate?
Pyruvate kinase
Which enzyme manage the conversion of 2 phosphoglycerate to phosphoenolpyruvate?
Enolase
Branched chain amino acids
Leucine, isoleucine, valine
A disorder characterized by defective breakdown of branched chain amino acids
Maple syrup urine disease
Which enzyme is affected in Maple syrup urine disease?
Branched chain alpha keto acid dehydrogenase
When does maple syrup urine disease usually manifest?
Within the first few days of life
Which type of diet do maple syrup urine disease should have?
Dietary restriction of branched chain amino acids, such as leucine
What diseases may lead by defective breakdown of tyrosine?
Hypertyrosinemia or alkaptonuria
What type of diet is recommended for patients with alkaptonuria?
Diet low in tyrosine and phenylalanine
Which enzyme is defective in hypermethioninemia?
Methionine adenosyltransferase
Which supplementations are required for treatment of classic homocystinuria?
Methionine restriction and cysteine supplementation
This illness classically results in dystonia and poor feeding as well as the mapple syrup scent
Maple syrup urine disease
What is Pompe disease?
Glycogen storage disease type II
Which enzyme deficiency causes Glycogen storage disease type II?
Acid alpha glucosidase (acid maltase)
Mechanism of action of Acid alpha glucosidase (acid maltase)
Breaking down glycogen within the acidic environment of lysosomes
Classic form of Pompe disease
Marked cardiomegaly, severe generalized hypotonia, macroglossia and hepatomegaly
Key distinguish of glycogen storage disease type II
Muscle biopsy shows Glycogen in lysosomes
Glycogen accumulation within lysosomal vacuoles is specific for…
Acid alpha glucosidase (acid maltase)
What does pyruvate kinase deficiency cause?
Chronic hemolytic anemia, splenomegaly, and iron overload as a result of impaired erythrocyte survival
A disease characterized by hemorrhages, subperiosteal hematomas, bleeding into joint spaces, gingival swelling, secondary periodontal infection, anemia, hyperkeratotic papular rashes, impaired wound healing and weakend immune response to local infections
Scurvy
Which is one of the most important functions of ascorbic acid?
Its activation of prolyl and lysyl hydroxylase precursors, both of which are necessary for the hydroxylation of procollagen
What characterizes zinc deficiency?
Acrodermatitis enteropathica, growth retardation and infertility
Which cells can’t utilize ketone bodies for energy?
Erythrocytes and other cells lacking mitochondria
These cells although they have mitochondria, they can’t utilize ketone bodies
Hepatocytes
Why hepatocytes can’t use ketone bodies?
Because they enzyme succinyl CoA acetoacetate CoA transferase (thiophorase)
Which is the most common cause of xeroderma pigmentosum?
Absence of UV specific endonuclease
Which is the function of UV specific endonuclease?
Recognizes distortions in the structure of DNA caused by thymine dimers, and subsequently excises stretches of single stranded DNA which contain these defects
Photosensitivity, poikiloderma, and hyperpigmentation in sun exposed areas and also posses a markedly increased risk of developing skin cancers
Xeroderma pigmentosum
Who is the only one that has 5’ to 3’ exonuclease activity?
DNA polymerase I
Which is the function of DNA polymerase I?
Remove the RNA primer (3’ hydroxyl group)
Once Removed the RNA primer (3’ hydroxyl group) by DNA polymerase I, who uses it to initiate DNA replication?
DNA polymerase III
What else does DNA polymerase I do?
Performs exonuclease excision and repair of damage to parent DNA
What is the purpose of 5’ to 3’ activity of DNA polymerase I?
Used to remove the RNA primer (which initiates DNA polymerizarion) and to remove damaged DNA
