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BB10004 > Glycogen Storage disease > Flashcards

Glycogen Storage disease Flashcards

1
Q

What is a glycogen storage disease

A
  1. Class of more than 10 distinct disorders of glycogen metabolism
  2. Results in either an increase or decrease in amount of glycogen
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2
Q

What are the 2 main tissues glycogen storage diseases affect

A
  1. Liver
  2. Muscle
  3. The storage sites of glycogen
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3
Q

Name 1 type of GSD

A
  1. GSD1

2. Type 1 glycogenosis

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4
Q

Who first discovered GSD1

A
  1. Von Grerke in 1929

2. Sometimes referred to as Grerke’s disease

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5
Q

What did Carl and Gerty Cori discover

A
  1. 1952

2. Demonstrated that GSD1 was due to deficiency of an enzyme- glucose-6-phosphatase

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6
Q

Describe the Cori cycle

A
  1. In the liver lactate is converted to pyruvate which is converted to glucose by gluconeogenesis
  2. This glucose forms glycogen in the muscle
  3. Glycogen forms pyruvate which is converted to lactate
  4. Lactate is transported in the blood to the liver
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7
Q

What is G6Pase

A
  1. Enzyme that is involved in the terminal step of glycogen breakdown and gluconeogenesis
  2. It catalyses the hydrolysis of glucose-6-phosphate to glucose + inorganic phosphate
  3. Water is added for this breakdown
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8
Q

Where are the 3 tissues that contain G6Pase

A
  1. Liver
  2. Kidney
  3. Intestint
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9
Q

Describe where G6Pase is in the liver

A
  1. Liver has 2 main cells- hepatocytes and bile duct cells (transport bile)
  2. G6Pase is in the hepatocytes
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10
Q

Where is G6Pase in the kidney

A
  1. In the proximal convoluted tubule cells
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11
Q

Describe the structure of the intesting

A
  1. Finger like projections which increase SA
  2. Goblet cells- mucous which lubricates the contents of the intestine
  3. Stem cells
  4. Paneth cells- contain lysozyme
  5. Pit cells- secrete prostaglandin
  6. Enteroendocrine- secrete hormones
  7. Enterocyte (absorptive)- G6Pase
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12
Q

Give a summary of the steps of glycogen breakdown

A
  1. (Glycogen phosphorylase) Glycogen + phosphate –> Glycogen(n-1) + glucose-1-phosphate
  2. (phosphoglucomutase) Glucose-1-phosphate glucose-6-phosphate
  3. (G6Pase) Glucose-6-phosphate + H2O –> Glucose + Pi
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13
Q

Show the steps of gluconeogenesis

A
  1. Lactate pyruvate
  2. Pyruvate –> fructose-6-phosphate
  3. (Phosphoglucoisomerase) Fructose-6-phosphate Glucose-6-phosphate
  4. (G6Pase) Glucose-6-phosphate + H2O –> Glucose + Pi
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14
Q

What does a mutase do

A
  1. Moves functional groups
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15
Q

Where is G6Pase localised

A
  1. In the endoplasmic reticulum
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16
Q

How does Glucose-6-phosphate enter the endoplasmic reticulum

A
  1. It is polar so needs help

2. Uses T1- a transporter

17
Q

What happens once G6P has entered the endoplasmic reticulum

A
  1. It can be hydrolysed by G6Pase to glucose and inorganic phosphate
18
Q

What happens once G6P has been hydrolysed

A
  1. The glucose is transported out of the ER by T3

2. The inorganic phosphate is transported out of the ER by T2

19
Q

What else is needed in the ER

A
  1. Stabilising protein in the membrane

2. Needed for intact G6Pase activity

20
Q

What is G6Pase an example of

A
  1. A multi-component enzyme system
21
Q

How is glucose removed from the cytoplasm out of the cell

A
  1. Using a facilitated transporter- GLUT2
22
Q

What is a problem with this method of glycogen breakdown

A
  1. Glycolysis occurs in the cytoplasm
  2. Glycolysis: G–>G6P
  3. Gluconeogenesis G6P–>G
  4. Can’t occur simultaneously as produce a futile cycle
23
Q

What is the name of Hexokinase IV in the lvier

A
  1. Glucokinase
24
Q

What does glucokinase do

A
  1. Catalysis conversion of Glucose –> G6P
25
Q

Describe what happens when there is high glucose in the hepatocyte

A
  1. Glucose is taken up and converted to G6P by GK

2. Goes through glycolysis

26
Q

Describe what happens when there is low glucose in the hepatocyte

A
  1. Want to produce glucose
  2. Entry of G6P into the ER and converted to G
  3. GK translocates into the nucleus (so it doesn’t convert G back to G6P)
27
Q

Why are there different forms of GSD1

A
  1. There are defects in different components of G6Pase system
28
Q

Name the different types of GSD1

A
  1. 1a- catalytic subunit defect
  2. 1b- glucose-6-phosphate trasporter defect (T1)
  3. 1c- Inorganic phosphate transporter defect (T2)
  4. 1asp- Stability protein (Sp) defect
29
Q

How common is GSD

A
  1. 1/100000 births

BB10004 (14 decks)

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