Glycolysis Enzymes and inhibitors/stimulators Flashcards
Hexokinase
- Catalyzes glucose to glucose-6-phosphate
- Stimulated by insulin
- Inhibited by Glucose-6-phosphate
Phosphofructokinase 1
- Catalyzes fructose-6-phosphate to fructose 1,6-bisphosphate
- Stimulated by hormones (fructose 2,6-bisphosphate, ADP, AMP)
- Inhibited by ATP, citrate
Pyruvate Kinase
- Catalyzes PEP to pyruvate (glycolysis)
- Stimulated by fructose 1,6-bisphosphate, insulin
- Inhibited by ATP
Pyruvate Carboxylase
- Pyruvate to OAA (done if acetyl CoA is high, and there i no need for more —convert to OAA so there is more to react with)
- stimulated by Acetyl CoA
- inhibited by insulin
PEP carboxykinase
-OXA to phophoenolpyruvate (gluconeogenesis)
- inhibited by insulin, AMP
- stimulated by Glucagon
Fructose 1,6-bisphosphatase
-Fructose1.6-bisphosphate to Fructose 6-phosphate (gluconeogenesis)
- Inhibited by Fructose 2,6, bisphosphate, AMP
- Stimulated be citrate
Glucose 6-phosphatase
G6P to glucose
Inhibited by insulin
Stimulated by Glucagon, epi
Glucose 6-phosphate dehydrogenase
G6P to phosphogluconolactone
-Inhibited by NADPH
Glucokinase
- Glucose to G6P (in glycogen breakdown) (hexokinase isozyme in the liver)
- NOT inhibited by G6P
- Stimulated by insulin
Phosphogulcomutase
G6P to G1P (part of glycogen breakdown)
UDP-glucosepyrophosphorylase
Glucose 1-P UTP to UDP (part of the glycogen breakdown pathway
Glycogen Synthase
Adds glucose to glycogen
- Inhibited by glucagon, epi
- Stimulated by insulin
Glycogen phosphorylase
Releases G1P units from glycogen
- Inhibited by insulin
- Stimulated by glucagon, epi
Debranching enzyme (just what is it)
Part of the glycogen breakdown
Branching enzyme (just what is it)
Part of the glycogen synthesis reactions
What is the equivalent enzymes for Hexokinase in glyconeogeneis?
Glucose-6-phosphatase
What is the equivalent enzymes for phosphofructokinase in glyconeogeneis?
Fructose 1,6 bisphophatase
What is the equivalent enzymes for Pyruvate kinase in glyconeogeneis?
There are two:
- PEP carboxylase
- Pyruvate carboxylase
Note that PEP carboxylase acts on OAO.
Phosphoglucomutase
Catalyzes reaction from G1P to G6P and vice versa. Used in the formation/breakdown of glycogen.
Type I GSD
Defect in the G6Pase–liver cannot export glucose, and thus builds up. Leads to hypoglycemia and increased liver stores
Type II GSD
Also known as Pomp disease
-Deficiency in acid maltase (alpha-gluconsidase). This enzyme is required for degradtaion of glycogen that slowly accumulates in the lysosome. Thus over time, the lysosome fills with glycogen and kills the cell. Death occurs by cardiac or respiratory failure.
Type III GSD
Cori disease
-A defect in glycogen debranching enzyme, causing glycogen granules to grow large because only the non-branched chain can be degraded.
Type V GSD
Also known as McArdle disease
-Defect in muscle glycogen phosphorylase, which renders the muscles unable to utilize stored glycogen.
Lead to exertional muscle weakness.
Na+/Glucose transporters: where are they found, what to the transport?
Found in the small intestine
Active transport of glucose, galactose from intestinal cell wall into the epithelial cells.
GLUT 1: where are they found, what do they transport?
All tissues
basal glucose/galactose uptake
GLUT 2: where are they found, what do theytransport?
Liver, intestines, and beta cells of the pancreas
Liver removes glucose/galgactose from blood
Intestine:release of glucose/galactose from epithelial cells into the circulation
Pancrease- regulation of insulin uptake
GLUT 3: where are they found, what do they transport?
All tissues
basal glucose/galactose uptake
GLUT 4: where are they found, what do they transport?
Muscle and adipose tissues
induced by insulin to take up glucose/galactose
GLUT 5: where are they found, what do they transport?
Small intestine, liver, others
Uptake fructose
What is Hunter disease? What is the defective enzyme, substrate built up, and inheritance pattern?
MR, skeletal abnormalities
Due to defective iduronate sulfatase
Builds up dermatan sulfate and heparan sulfate
XR
What is Hurler’s disease? What is the defective enzyme, substrate built up, and inheritance pattern?
Mr, Skeletal abnormalities
Due to defective alpha iduronase
Builds up dematan sulfate and heparan sulfate
AR
What is Sanflippo’s disease? What is the defective enzyme, substrate built up, and inheritance pattern?
MR, with slight physical abnormalities
Due to defective A, B, C, D root in different defects of heparan sulfate degradation
Builds up heparan sulfate
AR
PDH protein kinase
Inhibits the PDH cycle via phosphorylation
Activated by acetyl-CoA, NADH (increases PDH complex)
Inhibited by NAD, CoASH, and ADP
Citrate can be diverted from the CAC to produce what?
Acetyl -CoA to go to FA/sterol synthesis
Alpha ketoglutarate can be diverted from the CAC to produce what?
Glutamate to yield amino acids/purines
Succinyl-CoA can be diverted from the CAC to produce what?
Porphyrins (hemes/cytochromes)
Malate can be diverted from the CAC to produce what?
Pyruvate to produce alanine
OAO can be diverted from the CAC to produce what?
Phosphoenol-pyruvate to glucose OR
Aspartate to produce other amino acids.
Alpha keto glutarate dehydrogenase complex
Involved in the CAC
Inhibited by NADH and succinyl CoA
Isocitrate dehydrogenase
Involved in the CAC
Stimulated by ADP
Inhibited by NADH
What is the name of complex 1 in the ETC (named by the reaction it does)?
NADH-CoQ reductase
What is the name of complex 2 in the ETC (named by the reaction it does)?
Succinate CoQ reductase
What is the name of complex 3 in the ETC (named by the reaction it does)?
CoQH2 - Cytochrome C reductase
What is the name of complex 4 in the ETC (named by the reaction it does)?
Cytochrome Oxidase
What is the effect of Atractyloside?
Inhibits adenine nucloetide translocase
Fructosemia (not fructose urea) is a problem with what enzyme? What are the symptoms?
Aldolase B
Heptapmegally, liver failure, jaundice, inability to utilize glycogen
Galactosemia is a problem with what enzyme? What are the symptoms?
Galactokinase, UDP galactose uridyl transferase, or UDPG epimerse
Symptoms include MR, liver failure
What is protein phosphatase 1 (PP1)? How is it activated?
An enzyme in the liver, activated by insulin, that dephosphorylates proteins phosphorylated by PKA. (reverses glucagon effects)
Does insulin increase or decrease the liver’s uptake of glucose?
Neither, it always wants glucose
How does glucagon affect muscle cell glycolysis?
It doesn’t. There is no glucagon receptor.
Glucose-6-phosphate deficiency affects which metabolic pathway? Symptoms?
PPP
Hemolytic anemia due to inability to produce glutathione
For Tay-Sach’s disease, what is:
- the defective enzyme
- Accumulated lipid
- Presentation
- beta-hexosaminidase
- Ganglioside
- MR, blindness, death before 3 y.o.
For Gaucher’s disease, what is:
- the defective enzyme
- Accumulated lipid
- Presentation
- Beta-glucoside (cerebrosidase)
- Glucocerebroside
- Long bone defects, hepatosplenomegaly