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BioMedChem M3 > 30 - Enzyme Regulation > Flashcards

30 - Enzyme Regulation Flashcards

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

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

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

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

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

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

A

Catalyze the ADDITION of Phosphate groups
using ATP

in reversible phosphorylation

25
Q

PhosphaTASE Function

A

TASE = REMOVES phosphate

in reversible phosphorylation

26
Q

Phosphorylase Function

A

LASE = LACK ATP

DOES NOT USE ATP, uses Inorganic Phosphate

in reversible phosphorylation

27
Q

Examples of Phosphorylation REGULATION

Type of COVALENT Modifications

A
  • *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
Q

What does Acylation ADD? and to What?

A

Attaches FATTY ACIDS –> ESTER
range from acetyl groups (2C) –> Long chain FA’s

BULKY & Electrically NEUTRAL Group

as ANCHORS

29
Q

What is the FUNCTION of ACYLATION?

Type of COVALENT Modifications

A

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
Q

Types of ACYLATION use to help proteins to associate w/ MEMBRANEs

Type of COVALENT Modifications

A
  • *GPI Anchors**
  • -> external leaflet = RAFT

N-Terminal Mystic Acid Tail
SATURATED –> RAFT

C-terminol Sterols
​Saturated -> RAFT

Cys Acylation

Isoprenylation

31
Q

Lipids that go on RAFTS

Acylation

A

SATURATED lipid tails, RIGID / TIGHT
think Saturated = no kinks, full of double bonds

GPI-Anchored

Sterol-Linked

Palmitoylated intracellular

32
Q

Lipids that go on NON-raft regions

A

UN-saturated Tails
kinds = FLUIDITY

Prenylated

Palmitoyl

33
Q

Caveolae

A

SMALL CAVES associated with LIPID RAFTS
high in CHOLESTEROL & SPHINGOLIPIDS

involved in:
transmembrane transport & Signal transduction

34
Q

What does ACETYLATION ADD? and to what?

Type of COVALENT regulation

A
  • *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
Q

What is the FUNCTION of ACETYLATION?

Type of COVALENT regulation

A

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
Q

Acetylation & Metabolic State

A

Acetyl groups -> LYS
generated by the breakdown of FA’s / AA’s / CARBS

High Levels of Acetyl Groups = HIGH ENERGY

37
Q

Acetylation & CELL REGULATION

A

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
Q

Why do Cell proteins NOT last FOREVER?

A

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
Q

What is TURNOVER?

A

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
Q

2 Main Pathways of AA Recycling = TURNOVER

A

VACUOLAR
done by lysosomes / endosomes / ER

Cytoplasmic
done by ubiquitin / Proteasomes

  • Minor pathway* = caspases = cysteine proteases
  • *programmed cell death**
41
Q

What is PROTEOLYSIS?

A

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
Q

What are LYSOSOMES?

A

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
Q

Lysosomal Functions

A

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
Q

Lysosomal Diseases

A

Tay-Sachs** / **Pompe Disease

Defects in 1+ hydrolases –> “choke” the lysosome
w/ undigested large molecules –> disease

Buildup of undigested carbs –> stress the cell

45
Q

Cytoplasmic TURNOVER

A

“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
Q

Proteasome Inhibitors as DRUGS

A

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

BioMedChem M3 (8 decks)

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