L26: Allosteric Regulation and Commercialisation of enzymes

Cards (50)

  • What is the full name of the enzyme referred to as ATCase?
    Aspartate transcarbamoylase
  • Why is catalysis by ATCase considered the rate-limiting step in pyrimidine biosynthesis?
    Because it alters its catalytic activity in response to cellular levels of CTP and ATP
  • What effect does CTP have on ATCase activity?
    CTP decreases activity
  • What effect does ATP have on ATCase activity?
    ATP increases activity
  • What happens to the curve when 0.4 mM CTP is added?
    The curve shifts to the right
  • What happens to the curve when 2 mM ATP is added?
    The curve shifts to the left
  • What type of kinetics does ATCase exhibit?
    Non-Michaelis-Menten kinetics
  • What does increasing concentrations of CTP do to the apparent Km for aspartate?
    It increases the apparent Km for aspartate
  • How can allosteric interaction of ATCase be examined?
    Through structural studies using an inhibitor called PALA
  • What does PALA mimic in the study of ATCase?
    PALA mimics the reaction intermediate
  • What state does PALA stimulate the formation of in ATCase?
    The R, relaxed state
  • What is the activity level of the T state of ATCase?
    Low activity
  • What is the activity level of the R state of ATCase?
    High activity
  • What does allosteric regulation of ATCase involve?
    Equilibrium between the R and T states
  • What effect does CTP binding have on ATCase?
    It stimulates an allosteric shift to the T state
  • What effect does ATP binding have on ATCase?
    It stimulates an allosteric shift to the R state
  • What is the key enzyme in glycolysis mentioned in the material?
    Pyruvate kinase (PK)
  • What metabolic process occurs when glucose is in short supply?
    Gluconeogenesis
  • What is the relationship between glycolysis and gluconeogenesis?
    They are interconnected metabolic pathways
  • What is a futile cycle in metabolism?
    A cycle where glycolysis and gluconeogenesis occur simultaneously without net gain
  • What is feed forward activation in the context of pyruvate kinase?
    PK is activated by an early intermediate in glycolysis, FBP
  • What is feedback inhibition in the context of pyruvate kinase?
    PK is inhibited by an end product, ATP
  • What is the summary of allosteric regulation?
    • Allosteric regulation makes enzymes 'switchable'
    • Binding of effectors to secondary sites alters activity
    • Effectors can be activators or inhibitors
    • Changes operate through conformational changes affecting the active site
    • Displays non-Michaelis-Menten kinetics with co-operativity
    • Regulates flux of metabolites through pathways
  • What are some applications of enzymes mentioned in the material?
    Enzymes are used in farming, food industry, biosensors, and therapeutics
  • Why are shikimate pathways attractive targets for antimicrobial agents and herbicides?
    They are absent in animals
  • What is the mechanism of action of glyphosate as a herbicide?
    Glyphosate inhibits EPSP synthase in a competitive manner
  • What is the purpose of genetic engineering in crops to be Roundup resistant?
    To fuse the bacterial gene encoding CP4 EPSP synthase to a chloroplast signal peptide
  • What was the first Roundup Ready commercial crop?
    Roundup Ready soybeans
  • What are some pros and cons of glyphosate-resistant crops?
    Pros include reduced tilling and increased profits; cons include lower yield and potential increased herbicide resistance in weeds
  • What is the first approved GMO herbicide-resistant crop?
    Roundup Ready soybeans
  • What are some sources of enzymes for food applications mentioned in the material?
    Traditional sources include intact microbes
  • What are some applications of enzymes in the food industry?
    • Cheese making
    • High fructose corn syrup production
    • Aspartame production
    • Other food processing applications
  • What was the yield difference of Roundup Ready soybean crops compared to conventional varieties in 1999?
    Roundup Ready soybean crops had a 6.7% lower yield.
  • What are some approved GMO herbicide resistant crops and their uses?
    • Alfalfa: Animal feed (USA, approved 2005)
    • Canola: Cooking oil, margarine (USA, approved 1995)
    • Cotton: Fibre, cottonseed oil (USA, approved 1994)
    • Maize: Animal feed, high-fructose corn syrup (USA, approved 1995)
    • Soybean: Animal feed, soybean oil (USA, approved 1993)
    • Sugar Beet: Food (USA, approved 1998)
  • Who delivered Lecture 26 on enzymes in the context of the food industry?
    1. Robert Spooner.
  • What are the sources of enzymes for food applications?
    • Traditional: Using intact microbes (e.g., lactobacilli, S. cerevisiae, Aspergillus oryzae)
    • Increasingly: Enzymes or enzyme mixtures added to bioreactors
  • What is the structure of cow's milk and its main components?
    • Water: 85.5 - 89.5%
    • Fat: 2.5 - 6%
    • Protein: 2.9 - 5% (80% casein)
    • Lactose: 3.6 - 5.5%
    • Minerals: 0.6 - 0.9%
  • What role does chymosin play in milk structure?
    Chymosin cleaves κ-casein, destabilizing micelles and allowing milk to clot.
  • What is the enzyme classification number for chymosin?
    EC 3.4.23.4.
  • What are the benefits of using recombinant chymosin in cheese production?
    • High production yield
    • Better curd texture
    • Reduced bitterness
    • Suitable for kosher and halal certification