BioChem Enzymes Flashcards
Learn the 13 key enzymes involved in metabolism. Listing both their inhibitors and activators
Hexo/Glucokinase
First step of glycolysis. Phosphorylates glucose to glucose 6 phosphate. Locks glucose into cell
Hexokinase: Inhibited by product G6P
NB: Inhibition of PFK leads to build up of G6P
Glucokinase (in liver): has higher Km then hexokinase
NB: not inhibited by products
PFK
comitted step in glycolysis phorphorylates F6P->F16BP
Regulation: High ATP inhibits,
High AMP activates
Liver: Stimulated by F26BP F6P->F26BP by PFK2
inhibited by citrate
Pyruvate Kinase
Last step in glycolysis breaks down PEP to Pyruvate
Regulation: Inhibited by ATP, alanine
Activated by F16BP via feed forward mechanism
Pyruvate Dehdrogenase Complex
Large complex that converts pyruvate into Acetyl CoA after pyruvate has been shuttled into mitochondria
Reguatlion: phosphorylated and innactive
phorsphorylation increased by NADH, ATP and Acetyl CoA
Dephosphorylated and active. Phosphatase activity is increased by ADP, Pyruvate and Ca++
Isocitrate Dehydrogenase
Step in TCA cycle takes isocitrate to A-ketoglutarate with CO2 and NADH
Regulation: Inhibited by ATP and NADH. Leads to build up of citrate via aconitase converting isocit to cit
Cit inhibits PFK and acts as source of Acetyl CoA for FAS
Carnitine Shuttle
FA -> Acyl CoA via Acyl CoA synthetase
Carnitine shuttles acyl CoA across the inner mitochondrial membrane for FA degredation
Carnitine is recylced
Inhibited by malonyl CoA (precurrsor for FA synthesis)
Acetyl CoA Carboxylase
Enzyme that transforms Acetyl CoA to Malonyl CoA for FAS
Regulation: AMP dependent protein kinase inactivates
Phosphatase activates
Citrate activates even inactive form
Insulin Stimulates
Glucagon, Epinephrine inhibit ACC
Fatty Acid Synthase
Links malonyl CoA to Acetyl CoA to form long fatty acids. Need Malonyl ACP and Acetyl ACP
Adipose Tissue Lipase
Hormone Sensitive Lipase and Perilipase involved in FA degredation
Regulation: Epinephrine/ glucagon stimulate
Fructose 1,6 Biphosphatase
Enzyme that cleaves off phosphate in gluconeogenesis to form Fructose 6 Phosphate.
Inhibited by F26BP, AMP
Activated by citrate
Pyruvate Carboxykinase
First step in gluconeogenesis takes pyruvate to OAA. OAA can be shuttled out of the mitochondria in the form of malate. Uses ATP
Inhibited by ADP
Activated by Acetyl CoA
Glycogen Phosphorylase
Enzyme involved in breaking down glycogen
Takes piece of gylcogen and cleaves it to form glucose 1 phosphate
glucose 1 phosphate -> G6P via phosphoglucomutase
Regulation: Inhibited by G6P and ATP
Insulin leads to T state (less active) dephosphorylates a to b form
Glucagon leads to R state (more active)via phosphorylation of b form
Glycogen Synthase
Builds glycogen molecule from UDP-glucose monomers. Requires primer glycogenin
Regulation: Phosphorylated and deactivated
Dephosphorylated and active
Activated by G6P
Lipoprotein Lipase
Found in the lumen of the blood vessles. Breaks down FA carried on serum albumin. Allows for transport of FA into cells as FFA and monoacylglycerol
PEP Carboxykianse
Converts OAA into PEP. Uses GTP
Regulation: Inhibited by ADP