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BioMedChem M3 > 30 - Enzyme Regulation > Flashcards

30 - Enzyme Regulation Flashcards

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1
Q

Neostigmine

What does this DRUG inhibit?

A

Acetylcholinesterase

IRREVERSIBLE ENZYME INHIBITOR

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2
Q

Organo-arsenicals

A

Pyruvate Dehydrogenase

IRREVERSIBLE ENZYME INHIBITOR

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3
Q

D-cycloserine

A

Alanine Racemase

IRREVERSIBLE ENZYME INHIBITOR

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4
Q

Azaserine

A

Formylglycinamide Ribonucleotide AMINOTRANSFERASE

IRREVERSIBLE ENZYME INHIBITOR

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5
Q

4-hydroxy-androtenedione

A

AROMATASE

IRREVERSIBLE ENZYME INHIBITOR

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6
Q

Chloramphenicol

A

Peptidyl transferase

IRREVERSIBLE ENZYME INHIBITOR

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7
Q

5-fluorouracil

A

Thymidylate Synthase

IRREVERSIBLE ENZYME INHIBITOR

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8
Q

Disulfram

A

Aldehyde Dehydrogenase

IRREVERSIBLE ENZYME INHIBITOR

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9
Q

What is a Suicide Substrate?

and what are Examples?

A

The inhibitor is UNREACTIVE until the enzyme

tries to USE IT as a substrate.

covalent -> permenant inhibition

Ex.
Penicillin / Physotigmine / 5-fluorouracil

ASPIRIN is NOT a suicide substrate
it will REACT even W/O an active site

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10
Q

How is Acetylcholine broken down and why?

A

It is TOXIC if released in EXCESS

ACETYLCHOLINESTERASE = AChE

converts ACh to a less toxic choline

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11
Q

Acetylcholinesterase

A
  • *SERINE HYDROLASE**
  • inactivates Acetylcholine*

contains a key serine residue in the active site that reacts with a phosphorus-group of certain NERVE TOXINS
irreverisibly inactivates AChE

–> DEATH

Inhibitors of AChE = Parathion / Sarin / Dursban

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12
Q

Sarin

A

Covalent modification:
Irreversibly inhibits ACETYLCHOLINESERASE

  • *key serine** in AChE’s active site –> attacks Sarin’s P-group
  • irreverisbly inactivates AChE*
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13
Q

How do Heavy Metals cause TOXICITY?

Mercury / Lead / Silver
Iron + Copper

A

Heavy metals –> form tight bonds w/ SULFHYDRYL GROUPS
that are needed for catalytic activity or structural reasons

Cys / Disulfide bridges / Lipoate / CoA

Irreversibly inhibit catalysis function
&
Distort the STRUCTURE of the enzyme

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14
Q

Non-Covalent Regulation

A

Allosterism

&

Effectors

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15
Q

Types of COVALENT regulation

A
  • *Reversible**
  • *Phosphorylation / Energy Charge / Acetylation**

Irreversible
Proteolysis / Glycosylation

methylation / fatty acids

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16
Q

Types of COVALENT Modifications

A

Glycosylation

Methylation

Reversible Phosphorylation

Acylation (esp Acetylation)
FA’s

Proteolysis

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17
Q

What does GlycoSylation ADD? and TO WHAT?

Type of COVALENT Modifications

A

irreversible attachment of 1 or more SUGARs by glycosylases
in the golgi / ER

  • *Bulky / Polar / Solvated**
  • *RECOGNITION ELEMENTS**

Sugars-Oxygen –> SERINE residues

sugars-Nitrogen –> ASPARAGINE residues

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18
Q

What is the FUNCTION of GLYCOSYLATION?

Type of COVALENT Modifications

A

add sugars to:
Directing Enzyme** to its **Proper Cellular Location

for proper Folding/activation & release from cell

Also important for:
Cell-cell ADHESION
RECOGNITION by the immune system
PROTECTING proteins from attack

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19
Q

What does METHYLATION ADD? and to WHAT?

Type of COVALENT Modifications

Study These Flashcards
A

METHYL group to the terminal amino group on a LYSINE

may be REVERSIBLE, demethylases can remove methyl group

SAM = S-AdoMet
the MAJOR donor of in vivo methyl groups
Folate donates -Ch2 groups
Biotin carries the -COOH group

20
Q

What is the FUNCTION of METHYLATION?

Type of COVALENT Modifications

Study These Flashcards
A

methyl group –> Lysine

Affects the ELECTRICAL PROPERTIES on the amino groups

important for HISTONES –> in their role for gene expression

21
Q

What is SAM?

what are its functions

Study These Flashcards
A

S-AdenosylMethionine,
major donor for METHYLATION

Synthesis of:
epinephrine / phosphtidylcholine / creatine

Methylation of nucleic acid bases
Methylation of LYS RESIDUES IN HISTONES

22
Q

What does Reversible Phosphorylation ADD, & TO WHAT?

Type of COVALENT Modifications

Study These Flashcards
A

Kinase adds Phosphate groups using ATP
Ser / Thr / Tyr using the -OH sidechain
Phos-STT

Introduces a Charged / Bulky group that alters:

  • *Conformation** / state of aggreagetion
  • *Blocks sites**
  • *Attract/repel small molecues**

Appears in many
Energy-Producing** & **Energy-Consuming Pathways

23
Q

What is the FUNCTION of Reversible Phosphorylation?

Type of COVALENT Modifications

Study These Flashcards
A

phosphate -> STT (ser / thr / tyr) on -OH

ENERGY PATHWAYS
both Consuming & Producing

Kinase ADDS P w/ ATP

PhosphoTASES remove phosphate

PhosphoRYLASE do NOT use ATP -> use inorganic phosphate

24
Q

Kinase Function

Study These Flashcards
A

Catalyze the ADDITION of Phosphate groups
using ATP

in reversible phosphorylation

25
**PhosphaTASE Function**
**TASE =** **_REMOVES_** phosphate in **reversible phosphorylation**
26
**Phosphorylase Function**
**LASE** = **LACK ATP** DOES NOT USE ATP, uses **Inorganic Phosphate** in **reversible phosphorylation**
27
Examples of **Phosphorylation REGULATION** Type of COVALENT Modifications
* *_Metabolic Enzymes_** * *Glycogen synthase** / Acetyl CoA carbodylase / **PDH** **_Cytoskeletal Proteins_** desmin / vimentin / caldesmon * *_Nuclear Proteins_** * *CREB** / progestrone / **RNA** polymerase * *_Membrane_** **_Proteins_** * *Insulin receptor** / EGFR / B-adrenergic receptor
28
What does **Acylation** **ADD?** and to **What?**
Attaches **_FATTY ACIDS_** --\> **ESTER** range from **acetyl groups (2C)** --\> **Long chain FA's** **_BULKY_** & **Electrically _NEUTRAL_** Group as **ANCHORS**
29
What is the **FUNCTION of ACYLATION?** Type of COVALENT Modifications
Neutral / Bulky Fatty Acid Interfere with: **Protein-Protein Assocaition** **Conformational Change** / binding of amall molecules **LONG-CHAIN FA** = **hydroPHOBIC** --\> can **_Hold Proteins in Membrane_** an maybe **direct the polypeptide** to proper cell location
30
**Types of ACYLATION** use to help **proteins to associate w/ MEMBRANEs** Type of COVALENT Modifications
* *_GPI Anchors_** - -\> external leaflet = RAFT **_N-Terminal Mystic Acid Tail_** SATURATED --\> RAFT **C-terminol Sterols** ​Saturated -\> RAFT **Cys Acylation** **Isoprenylation**
31
Lipids that go on **RAFTS** Acylation
**_SATURATED_** lipid tails, **RIGID / TIGHT** think Saturated = no kinks, full of double bonds **_GPI-Anchored_** **_Sterol-Linked_** **_Palmitoylated_** intracellular
32
Lipids that go on **NON-raft regions**
**_UN-saturated Tails_** kinds = **FLUIDITY** **_Prenylated_** **_Palmitoyl_**
33
**Caveolae**
**_SMALL CAVES_** associated with **LIPID RAFTS** high in **CHOLESTEROL & SPHINGOLIPIDS** involved in: **transmembrane transport & Signal transduction**
34
What does **ACETYLATION ADD?** and to what? Type of COVALENT regulation
* *Acetylases** add **_2-Carbon FA_** - -\> **END** of the side chain of **_Lys**_ _**(_amide linkage)** * DEacetylases REVERSE this process* A **type of Acylation,** as common as phosphorylation is often ***_REVERSIBLE_****, like phosphoylation*
35
What is the **FUNCTION** of **ACETYLATION**? Type of COVALENT regulation
2-Carbon FA --\> **LYS** side chain, amide linkage **LOSES the + Charge on LYS** affects: **substrate binding / assocation** **_CHANGE IN ENZYME ACTIVITY_** activated or inhibited (MDH in TCA / SDH in TCA) **_Metabolic State_** **_Cell Regulation_**
36
**Acetylation & Metabolic State**
Acetyl groups -\> **LYS** generated by the **breakdown of FA's / AA's / CARBS** _**High Levels of Acetyl Groups** = **HIGH ENERGY**_
37
**Acetylation & CELL REGULATION**
2C-FA -\> LYS * *acetyltransferase / deacetylases** often found in * *nucleus / mito / cito** **_Metabolism_** ENZYMES * *_Cytoskeleton_** * *a-tubulin**, is aceytlated -\> regulates STABILITY of microtubules * *_GENE EXPRESSION_** * *histones** -\> **various tx factors + coregulators**
38
Why do **Cell proteins NOT last FOREVER?**
**Damaged / MISfolded** Need to be **REMOVED** as a part of the **cell cycle** or to **CONTROL** a **metabolic pathway** or as a part of **Programmed Cell Death = Apoptosis** for **_TURNOVER**_ = _**AA's can be RECYCLED_**
39
What is **TURNOVER?**
the **_RECYCLING_** of **AA's from proteins** **Protein Breakdown / Re-Conversion** to **Short Peptides / AA's** 2 main pathways: **Vacuolar / Cytoplasmic** *cysteine proteases = caspases*
40
**2 Main Pathways of AA Recycling = TURNOVER**
**_VACUOLAR_** done by **lysosomes** / **endosomes** / **ER** **_Cytoplasmic_** done by **ubiquitin / Proteasomes** * **Minor pathway*** = **caspases** = cysteine proteases * *programmed cell death**
41
What is **PROTEOLYSIS**?
**_AMIDE BOND CLEAVAGE_** a type of **_Cytoplasmic_ Turnover** = **Inactivate protein/enzyme** *issue is balancing & the costs of new synthesis* Generally **_irreversible_ modification** *unlike phosphorylation & acetylation* Can **ALSO lead to ACTIVATION** inactive precursor -\> cleaved to produce an ACTIVE anzyme in _digestive / blood clotting / **insul**_
42
What are **LYSOSOMES?**
Type of **_VACUOLAR_** **Turnover**: **Hydrolytic Sacs** **ATP-Driven Proton PUMP --\> _ACIDIFIES INSIDE_** **Acid Hydrolases** for: _proteins / carbs / nucleic acids / lipids_ **_active ONLY @ ACID PH_**
43
**Lysosomal Functions**
Large molecules brought in by **vesicles** that **merge w/ lyososme membrane** **_METABOLITE TRANSPORTERS_** expel the **resulting monomers** primary route for **recycling / turnover** of: **AA / Sugars / Simple Lipids**
44
**Lysosomal Diseases**
**_Tay-Sachs**_ / _**Pompe Disease_** Defects in **1+** **hydrolases** --\> **"choke" the lysosome** w/ **undigested large molecules** --\> **disease** Buildup of undigested carbs --\> stress the cell
45
**Cytoplasmic TURNOVER**
"**Mark & Chew**" 1st stage = **_UBIQUINATION_** **marks** the proteins for degradation, w/ ubiquitin (protein) 2nd = **_PROTEOSOMAL_** action * *proteasome** --\> **hydrolyzes PEPTIDE bonds** - -\> releases **AA's & short peptides**
46
**Proteasome Inhibitors as DRUGS**
Proteasomes **regulate cell cycle** by **degrading key proteins** used for **rapid synthesis** / **signal proteins** Disrupting proteasomes -\> **HALT Growth / proliferation** Applications of *inhibition of proteolytic Activity:* * *Anticancer / Antiviral** Drugs * *Anti-Inflammatory / Anti Tuberculosis** **Ishema / Stroke** damage alleviation

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