Finals NUTR Enzymes

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emmayarewhy
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Finals NUTR Enzymes
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2012-12-13 20:21:01
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final nutr enzymes
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  1. AMPK
    A WIDE VARIETY OF ACTIVITIES. 
  2. Glycogenesis

    Glycogen synthase
    Rate-determining enzyme for glycogenesis.

    Activated by insulin (PP1); inhibited by PKA (via cAMP & glucagon/epinephrine)
  3. Branching Enzyme
    Glycogenesis

    Chops off 6-8 glucoses off of the linear chain and attaches as a1,6 bond as branch. 
  4. Glycogen phosphorylase
    Rate-det enzyme for glycogenolysis

    Activated by PKA, cAMP, glucagon/ep. Inhibited by insulin (PP1)
  5. Glucosyl transferase
    • Glycogenolysis
    • Responsible for cutting off 3 glucose units on a 4 glucose chain and transferring them to linear branch so that glycogenolysis can continue. 
  6. Debranching Enzyme
    Glycogenolysis:

    Chops off a1,6 bond - last glucose - and releases as free glucose. 
  7. Glucose 6 Phosphatase
    • Glucose 6 P--> free glucose.
    • Seen in glycogenolysis, gluconeogenesis

    Not in muscle!
  8. PKA
    Glucagon/Epinephrine --> activate adenylyl cyclase to synthesize cAMP which activates synthesis of PKA. Seen in many metabolic rxns.

    • - Glycogenolysis/glycogenesis
    • - Gluconeogenesis 
  9. Protein Phosphatase 1
    Activated by insulin

    Seen in both glycogen metabolism
  10. Ca2+-dep kinase
    Seen in muscle during glycogenolysis. 
  11. Glucokinase vs. Hexokinase?
    - Km?
    - Vmax?
    - Tissues?
    - Activation/Inhibition?
    - What is important about glucokinase's Vmax?
    Glucokinase has higher km (specificity) and higher capacity to process glucose

    Glucokinase is found in the liver while hexokinase is found in most tissues.Activated by glucose

    Glucokinase has a high Vmax, allowing liver to remove lots of glucose from blood post-prandially to prevent hyperglycemia.

    Glucokinase has absolutely no feedback inhibition, while hexokinase is allosterically inhibited by G6P (fastest regulation).
  12. PFK-1
    • Activated by: AMP, F2,6BP
    • Inhibited by: ATP, citrate
  13. Pyruvate kinase
    Glycolysis: PEP---> Pyruvate

    Inhibited by glucagon
  14. Glucose 6 dehydrogenase
    Main enzyme in PPP
  15. Pyruvate carboxylase
    Substrate --> product?
    Requires?
    Is this enzyme found in muscle? If so, what's the diff?
    Activated by? Inhibited by? 1 each.
    • Pyruvate --> OAA
    • Requires B7 
    • Yes, but muscle does not do GNG - instead pyruvate carboxylase is used to make OAA for TCA cycle for oxidative phosphorylation.

    Activated by: Acetyl CoA (elevated levels of acetyl CoA signal metabolic state in which more OAA is needed - when OAA is needed for synthesis of glucose in liver & kidney). At low levels of Acetyl CoA --> PDH is active for TCA cycle.
  16. PEPCK
    Driven by?
    Regulation of PEPCK?
    • OAA --> PEP
    • Driven by GTP (combined actions of pyruvate carboxylase & PEPCK --> energetically favorable pathway from pyruvate --> PEP).

    Gene transcription regulated by glucagon:insulin ratio. Glucagon increases PEPCK.Adiponectin & insulin decrease PEPCK
  17. F1,6bisphosphatase

    Activated by? 3
    Inhibited by? 3
    F1,6BP --> F6P

    • Activated by:  (1)ATP, (2) glucagon (cAMP, PKA, p'lated form of PFK-2/FBP-2 allows FBP2 domain to be active. Decreased levels of F2,6BP decreases inhibition of F1,6BPtase, increasing GNG. 
    • Inhibited by: AMP, insulin, (PFK-2 --> F2,6BP).
  18. Glucose-6-Phosphatase
    Found in which 2 organs?
    Regulation?
    • Glucose 6 P --> Free glucose. 
    • - Found only in liver and kidney

    Adiponectin decreases its gene transcription
  19. HMG CoA Synthase
    Acetyl CoA + acetoacetate --> HMG CoA
  20. HMG CoA Reductase

    Regulation?
    HMG CoA --> Mevalonate - Rate limiting enzyme for cholesterol synthesis. 

    Sterols are dependent on regulation of gene expression (SREBP-2 binds to SRE of reductase gene).
  21. ACAT/LCAT
    Esterifies cholesterol into cholesteryl esters.

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