• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

Card Range To Study



Play button


Play button




Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

13 Cards in this Set

  • Front
  • Back
Control of Amount of Active Enzyme
1) Tissue Characteristics
-differentiation due to differential gene expression; organs have different metabolic roles

2) Alterations in rate of protein synthesis and/or breakdown (Major Site of Regulation)
Control of Amount of Substrate
1) Transport
a) membranes cause compartmentalization
b) selective permeability properties exist in a given membrane type due to expression of specific transporters
c) substrate concentration < Km and therefore in the first order range (changes in concentration cause changes in reaction rate)

2) Interactions with other metabolic systems
- branch points; can drain or replenish substrate levels thereby altering enzyme activity
Non-covalent Mechanisms (allosteric) which affect protein activity
1) readily reversible
2) dependent on presence & concentration of modifiers
3) rapid --> seconds
Effects of Catalytic Activity at Constant Enzymatic & Substrate Concentrations
1) Activators & Inhibitors (Allosteric) --> Major Site of Regulation
2) Modification of Catalytic capacity of enzymes (active-inactive conversions) --> Major Site of Regulation
3) Environmental (pH, osmotic effects, etc.)
Covalent Mechanisms which affect Protein Activity
1) Stable, not readily reversible
2) Usually require 2 enzymes, one to add the group & one to remove it
-Exception to this is proteolytic modification which is completely IRREVERSIBLE
3) Moderately Fast --> minutes

Ex. Proteolytic Modification
a) conversion of precursor to active forms; this is a very improtant mechanism in blood clotting, in peptide hormone synthesis, and in digestion
b) Inactivation of enzymes via proteolytic digestion (degradation, turnover)
-catalyzed by ADP ribosyl transferases, which among others are important in the action of certain potent bilogical toxins (cholera, diptheria, & pertussis)

A) Mechanism
-transfer of ADP ribose from NAD to arginine ot other amino acid residues

B) Examples
-Guanyl nucleotide binding proteins of adenylate cyclase are ADP ribosylated by baterial toxins which have enzyme activity
Cholera Toxins
-activates Gs
-catalyzes the ADP ribosylation of Gs & some other G proteins
Pertussis Toxin
-inhibits Gi
Gs Protein
-turns on adenylate cyclase
Gi Protein
-turns off adenylate cyclase
Source of ADP ribose
-->nicotinomide is the product
-Phosphate from ATP (or GTP) is covalently attachems to serine, threonine, or tyrosine residue of proteins
-can cause a change in Km, Vmax, or in the sensitivity of the enzyme to an allosteric effector
-accomplished by --> PROTEIN KINASE
cAMP - dependent protein kinase (protein kinase A, PKA)
-PKA is activated by cAMP
-phosphorylates many different proteins