Regulation of Metabolism Flashcards
formation and degradation of fructose 26 bp; function?
catalyzed by PFK2 and FBPase-2 (same protein- 2 different active sites); when glucose is in abundance, PFK2 is activated and level of F26BP increases, increasing glycolysis; when glucose levels are low, FBPase-2 is activated and F26BP decreases, inhibiting glycolysis
example of feed forward activation
F16BP is allosteric activator of liver pyruvate kinase (PEP–> pyr)
pyruvate dehydrogenase kinase inhibited by
pyruvate so that pyruvate dehydrogenase remains in active form and can make acetyl coa for the TCA cycle
PEP is a feedback____
inhibitor of phosphofructokinase
why is phosphofructokinase so strictly regulated and by what?
because PFK takes F6P to F16BP and that is the first solely glycolytic step in glycolysis
glucose-alanine cycle
glucose turns to pyruvate which then using AA in metabolism makes alanine which goes to the liver; the nitrogen is taken out of alanine into urea; and the carbons are then used to build glucose and sent back to muslce
urea cycle
takes nitrogen off of amino acids, the carbons on amino acids are then used to build glucose and other macromolecules; urea exits from body
cori cycle
glucose and glycogen turn into lactate in the muscle, lactate taken back to liver and via gluconeogenesis turns into glucose which is taken back to muscle
why does hexokinase get preferential treatment?
low Km- high affinity for glucose because it is in most cells (specifically brain) and the brain needs glucose; glucokinase has lesser affinity (high Km) for glucose because it can also use fructose and other items for energy
ex of covalent modification
phosphorylation (PFK2 and FBPase-2)
acetylation
regulatory cascade
hormones (epinephrin) activates cAMPs which are 2nd messengers- results in signaling cascade–> immediate action (amplification)
regulatory casecade coordinates both ON and OFF..how?
In addition to phosphorylating and activating phosphorylase kinase (activating glycogen phosphorylase), protein kinase A adds a phosphoryl group to glycogen synthase, which leads to a decrease in enzymatic activity. This important control mechanism prevents glycogen from being synthesized at the same time that it is being broken down.
hormonal regulation of F26P
low blood–> increased glucagon secretion–> increasing cAMP–> increased enzyme phosphorylation–> activation of FBPase-2 and inactivation of PFK2–> decreased F26P–> inhibition of PFK and activation of FBPase–> increased gluconeogenesis
what happens when regulation is bypassed in alcohol metabolism?
fatty liver- formation of acetyl coa via alcohol dehydrogenase pathway–> acetyl coa becomes malonyl coa and continues to synthesize fatty acids
