Pyridoxal Phosphate in Aminotransferases
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Questions and Answers

What is the coenzyme form of pyridoxine required for the enzyme's activity?

  • Amino acid
  • Vitamin B6
  • Pyridoxal phosphate (correct)
  • Pyridoxine

    • What is the function of pyridoxal phosphate in aminotransferases?

  • Final transporter of amino groups
  • Initial donor of amino groups
  • Intermediate carrier of amino groups (correct)
  • Terminal acceptor of amino groups

    • What type of linkage is formed between pyridoxal phosphate and the ε-amino group of a Lys residue?

  • Aldimine (Schiff base) linkage (correct)
  • Peptide bond
  • Hydrogen bond
  • Disulfide bond

    • What is the form in which amino groups are transported in blood to the liver?

    <p>Glutamine, glutamate, and alanine</p> Signup and view all the answers

    Where are the amino groups of amino acids from dietary proteins and cellular proteins incorporated into?

    <p>Glutamate</p> Signup and view all the answers

    What is the result of the formation of a Schiff base between pyridoxal phosphate and the amino group of the amino acid?

    <p>Release of the enzyme</p> Signup and view all the answers

    What is the product of the transamination reaction between glutamate and pyruvate in muscle?

    <p>Alanine and α-ketoglutarate</p> Signup and view all the answers

    What is the purpose of the Glucose-Alanine Cycle?

    <p>To transport amino groups from muscle to liver</p> Signup and view all the answers

    What is the enzyme involved in the transamination reaction between alanine and α-ketoglutarate in the liver?

    <p>Alanine aminotransferase</p> Signup and view all the answers

    What is the fate of pyruvate produced in the liver through gluconeogenesis?

    <p>It is transported to muscle and converted to alanine</p> Signup and view all the answers

    What is the purpose of glutamine synthetase in extrahepatic tissues?

    <p>To convert glutamate to glutamine</p> Signup and view all the answers

    What is the byproduct of the deamination of glutamate in the liver?

    <p>NH4+ and α-ketoglutarate</p> Signup and view all the answers

    What is the term used to describe the connection between the urea cycle and the citric acid cycle?

    <p>Krebs bicycle</p> Signup and view all the answers

    Where are the enzymes fumarase and malate dehydrogenase also present as isozymes?

    <p>Cytosol</p> Signup and view all the answers

    What is the product of the hydration of fumarate in the cytosol?

    <p>Malate</p> Signup and view all the answers

    What is one possible fate of oxaloacetate?

    <p>It can undergo transamination to aspartate</p> Signup and view all the answers

    At what two levels can the activity of the urea cycle be regulated?

    <p>At the level of enzyme synthesis and control by allosteric regulation</p> Signup and view all the answers

    What enzyme's rate of synthesis can control the activity of the urea cycle?

    <p>Carbamoyl phosphate synthetase I</p> Signup and view all the answers

    What is the purpose of supplementing the diet with benzoate and phenylacetate in Carbamoyl phosphate synthetase I and ornithine transcarbamoylase deficiency?

    <p>To excrete excess nitrogen in the form of hippurate and phenylacetylglutamine</p> Signup and view all the answers

    Why is a protein-free diet not a treatment option for deficient enzymes?

    <p>Because humans cannot synthesize essential amino acids</p> Signup and view all the answers

    What is the difference between essential and non-essential amino acids?

    <p>Essential amino acids are provided in the diet, while non-essential amino acids are synthesized by humans</p> Signup and view all the answers

    What is a symptom of ammonia intoxication?

    <p>Tremor</p> Signup and view all the answers

    What is a possible reason for the toxic effect of ammonia?

    <p>A decrease in the formation of ATP by citric acid cycle</p> Signup and view all the answers

    What is a common symptom of hyperammonemia?

    <p>Lethargy</p> Signup and view all the answers

    What is the product of the cleavage of the aromatic ring of homogentisate?

    <p>4-maleylacetoacetate</p> Signup and view all the answers

    What is the name of the disease caused by a deficiency of phenylalanine hydroxylase or its tetrahydrobiopterin cofactor?

    <p>Phenylketonuria</p> Signup and view all the answers

    What is the end product of the reaction catalyzed by maleylacetoacetate isomerase?

    <p>4-fumarylacetoacetate</p> Signup and view all the answers

    Which enzyme is responsible for the hydrolysis of 4-fumarylacetoacetate to fumarate and acetoacetate?

    <p>Fumarylacetoacetase</p> Signup and view all the answers

    What is the characteristic of the urine in individuals with phenylketonuria?

    <p>Mousey odor</p> Signup and view all the answers

    What is the alternative pathway of phenylalanine metabolism in individuals with phenylketonuria?

    <p>Transamination with pyruvate</p> Signup and view all the answers

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