Protein Phosphatases Flashcards
Is the protein kinase reaction reversible or irreversible?
Irreversible, protein phosphatases induce a different reaction, hydrolysis
Why is phosphorylation irreversible?
Since it produces ATP and hydrolysis by protein phosphatases does not
What is a phosphorylase?
Causes phosphorylation of a substrate
What is phosphorylase kinase?
Phosphorylates the phosphorylase
What is PP1
Phosphorylase phosphatase - dephosphorylates phosphorylase
How is Src activated?
Dephosphorylation of pTyr508
Phosphorylation of Tyr397
How many kinases are in the kinome?
> 500
How are kinases and phosphatases families different?
Most kinases are similar, phosphatases are different based on their catalytic mechanisms and amino acid sequences
How many phosphatase phynogenic trees are there?
10
What family due tyrosine phosphatases belong to?
CC1
What are dual specificity phosphatases?
They can be serine/threonine phosphatases or tyrosine phosphatases
Which dual specificity phosphatase is different and why?
PTEN
It can be a lipid or protein tyrosine phosphatase
What do phosphatases recognise?
Molecular features instead of consenus sequences around the phosphorylated site
What is the difference between protein tyrosine phosphatase catalytic pockets to serine/threonine phosphatases?
Tyrosine phosphatase catalytic pockets are deeper than serine/threonine phosphatase catalytic pockets
Why do tyrosine phosphatases have deeper catalytic pockets than serine/threonine phosphatases?
Phospho-tyrosine is a big molecule
Describe the active site of PP1
Contains a bimetal centre Bridged by a water molecule, which is displaced by the binding of phosphate Has 3 grooves: - an acidic groove - a C-terminal groove - a hydrophobic groove
What is the mechanism of the phosphate in PP1?
The phosphate undergoes nucleophilic attack by a hydroxyl ion
Histidine125 provides a proton to the alcohol group
Metal ions are important in coordinating this mechanism
What is the inhibitor of PP1?
Inhibitor 1 and 2
What is the inhibitor of PP2A?
Okadaic acid
What is the inhibitor of PP2B?
Trifluoperazine
What is the inhibitor of PP2C?
EDTA
What is the activator of PP2B?
Ca2+-calmodulin
What is the activator of PP2C?
Mg2+
Where is PP2B abundant?
In the brain