Protein Phosphatases

Question 1

What do protein phosphates do on protein side chains?

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Answer 1

catalyzes the removal of covalent phosphate modification

Question 2

Dephosphorylation is thermodynamically ____.

Answer 2

unfavorable

Question 3

Protein phosphatases (~140) are divided into ____ and ____.

Answer 3

pSer/Thr phosphatases (28);
pTyr phophatases (107)

Question 4

pSer/Thr phosphatases are divided into which classes?

Answer 4

• PPP (13) - Class I
• PPM (10) - Class II
• FCP (5) - Class III

Question 5

pTyr phosphatases are divided into which two subcategories?

Answer 5

• Cys-based (103)
• Asp-based (4)

Question 6

Cys-based, pTyr phosphatases are categorized into what three classes?

Answer 6

• Class I (99)
• Class II (1)
• Class III (3)

Question 7

Class I, Cys-based, pTyr phosphatases are categorized into what two classes?

Answer 7

• classical PTPs (38)
• dual specificity phosphatases (61)

Question 8

PPP

Answer 8

phosphoprotein phospatase
* metalloenzymes binding to a pair of metal ions (Fe, Zn, Mn)
* allow versatility of interaction in various locations and pathways

Question 9

PPM

Answer 9

protein phosphatase Mg2+
* metalloenzymes with Mg2+ requirement
* catalysis via activating water

Question 10

FCP

Answer 10

component of RNA polymerase II CTP phosphatase
* dependent of Mg2+ for catalysis
* dephosphorylates C-terminus of RNA polymerase
* plays role in regulating growth factor signaling pathways

Question 11

What is the basic mechanism for serine/threonine phosphatases?

Answer 11

• bi-metal active site
• phosphoric group is transferred to water in one step

Question 12

What is a holoenzyme complex?

Answer 12

It is a broad range of distinct pathways and localization to diverse areas of the cell. Ser/Thr phosphatases can form these.

e.g. all the possible partners that PP1 can bind with

Question 13

Cys-based PTPs have a catalytic motif comprising ____ and ____.

Answer 13

cystine; arginine

Question 14

When cystine acts a nucleophile, it attacks the substrate, ____, and forms a covalent phosphocysteine.

Answer 14

phosphotyrosine

Question 15

• acts as a transition-state analog of phosphate
• inhibitor of PTPs and can have therapeutic properties

Answer 15

vanadate

Question 16

Cys-PTP, Class I can be divided into ____ (38) and ____ (61).

Answer 16

classical PTPs;
Dual-specificity phosphatases