Enzymes Flashcards
Acid Sphingomyelinase
breaks down sphingomyelin into ceramide and phosphorylcholine
Na/K ATPase
Na moves out, K moves in
Sodium Calcium Exchanger
Na moves in, Ca moves out. Coupled with Na/K pump
GLUT 1
ubiquitous, high expression in RBCs and brain, high affinity for glucose
GLUT 2
found in liver and pancreas, low glucose affinity
GLUT 3
main transporter in neurons, high affinity
GLUT 4
skeletal muscle, heart, and adipose, insulin dependent, lower affinity for glucose
Hexokinase/Glucokinase
Hexo-found every where, Gluco-found in liver, pancreatic B cells
Regulatory protein that traps glucose inside cells
Inhibited by Glucose 6P, glucagon, fructose6p
Promoted by Glucose, Fructose1P and Insulin
Phosphoglucose Isomerase
Isomerization of G6P to F6P
PFK-1
Rate limiting step, inhibit by ATP and citrate, F6P to F1,6BP
Aldolase A
Cleaves F1,6BP into DHAP and G3P
Triose phosphate isomerase
Interconverts DHAP and G3P
Glyceraldehyde 3P Dehydrogenase
phosphorylate G3P, creates NADH
Phosphoglycerate kinase
Conversion of 1,3BPG to 3PG
Pyruvate kinase
Formation of 2pyruvate, releases 2 ATP
How is glucokinase regulated?
F6P promotes translocation of GK to the nucleus, High glucose promotes GK release from GK-RP
How is PFK-1 regulated?
RATE LIMITING, F6P to F-1,6-BP, it is inhibited by ATP and citrate, it is activated by AMP and F2,6BP (formed by PFK-2), dephosphorylated form is favored by insulin, phosphorylated form is favored by glucagon
How is pyruvate kinase regulated?
PK catalyzes the conversion of PEP into pyruvate. It is activated by F1,6BP and insulin. It is inhibited by ATP, Ala, and glucagon, active form is dephosphorylated.
What are the four enzymes in gluconeogenesis that bypass the regulated enzymes of glycolysis?
Pyruvate carboxylase, PEP carboxykinase, F1,6BPase, Glucose 6-phosphatase
How is pyruvate carboxylase regulated?
Catalyzes the first step of of gluconeogenesis (pyruvate to OAA), it requires a biotin cofactor and is activated by acetyl CoA and cortisol
Mitochondrial malate dehydrogenase
OAA reduced to malate
Phosphoenolpyruvate carboxykinase (PEPCK)
decarboxylate and phosphorylate OAA to PEP, activated by cortisol, glucagon, and thyroxine
Fructose 1,6 Bisphosphatase
RATE LIMITING, F1,6BP to F6P, activated by cortisol and citrate, inhibited by AMP and F2,6BP
Glucose 6-Phosphatase
dephosphorylation to form glucose, only in liver, kidneys, SI, and pancreas. Activated by cortisol
Aldose reductase
reduces sorbitol to glucose
Sorbitol dehydrogenase
oxidizes sucrose to fructose
Glucose 1P Uridyltransferase
able to convert galactose 1-P to glucose 1-P by transferring UDP from UDP-glucose to galactose.
Lactase
Latate to glucose and galactose
Galactokinase
Converts galactose to galactose 1-P
G6P dehydrogenase
RATE LIMITING, Reduced glutathione to oxidized glutathione, produces 2 NADPH
Transketolase
TPP required as coenzyme, catalyzed transfer of 2C
Transaldose
catalyzes transfer of 3C segments
Phosphoglucomutase
isomerizes G6P to G1P
UDP-glucose pyrophosphorylase
G1P to UDP-Glucose
Glycogen synthase
RATE LIMITING, UDP-glucose to non reducing end of glycogen chain, dephospho form active, phospho form inactive
glucosyl (4:6) transferase
reattaches glycogen chain broken off (after 11 residues) via a-1,6 bond
glycogen phosphorylase
RATE LIMITING in chain shortening, cleaves glucose residues off non-reducing end as G1P, uses vitamin B6, dephospho form is inactive, phospho form is active