BIOL213 Lecture Notes - Lecture 18: Post-Translational Modification, Metabolic Pathway, Enzyme

113 views7 pages
24 May 2018
School
Department
Course
Professor
Lecture 18 Enzyme Regulation
Enzyme regulation:
Key enzymes in each metabolic pathway are regulated so that each type of
molecule is produced in a quantity appropriate to the current requirements of the
cell. If enzymes were not regulated, metabolic pathways would be way to chaotic.
In metabolic pathways, there are regulatory enzymes which may experienced an
increase or decrease in catalytic activity in response to signals.
In multi-step, multi-enzyme systems, the first enzyme is often the regulatory
enzyme. Other enzymes are often n excess. This prevents there from being a lot of
the last enzyme (E) and very little to the first enzyme (A).
Often the first enzyme is a large enzyme as well.
There are many different factors that affect the regulation of enzyme activity, not
just substrate concentration. These factors include signals coming in, allosteric
regulation, regulatory proteins, and mRNA translation.
Feedback control:
In most multi-enzyme systems, the regulatory enzyme is inhibited by the end-
product. The last enzyme acts on the first enzyme to regulate its activity. Too
much of enzyme F acts negatively to enzyme A > negative feedback. Opposite
occurs if we have not enough F.
This feedback is an example of allosteric regulation - this is post-
translational modification of enzymes.
This negative feedback occur when the amount of product exceeds the cells
requirements.
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 7 pages and 3 million more documents.

Already have an account? Log in
Lecture 18 Enzyme Regulation
Example of feedback control: aspartate trans-carbamoylase catalyses the first step
in the synthesis of nucleotides from aspartate. This enzyme is inhibited by the end
product of this metabolic pathway, CTP.
Regulatory enzymes:
these increase o decrease catalysis in response to specific signals, and they do this
to control the rate of metabolic pathways.
The first enzyme in most multi-step is the regulatory enzyme.
This regulation is controlled by:
-allosteric modulation
-reversible covalent modification
-proteolytic cleavage (proteolysis).
Allosteric enzymes:
Allosteric control is regulation of an enzyme that occurs when a molecule
interacts at a site other than the active site, and in this way influences the activity
of the enzyme. It is not a the same as inhibition (this occurs when something
binds to active site).
Allosteric modulation can either be stimulatory or inhibitory.
Stimulatory (positive) modulators increase the enzyme’s affinity for the substrate.
The opposite occurs in inhibitory (negative) modulation.
Allosteric modulation leads to conformational changes on the enzyme
Allosteric enzymes are generally larger than non-allosteric enzymes. Most of them
have two or more subunits.
Binding of the modulator results in formational changes that affect the subsequent
activity of other sites on the proteins > affects the active site.
Advantages:
-serve as a really good way of affecting enzyme activity other than inhibition
-sensitive to the immediate environment
-rapid and reversible
-provides sophisticated control of the activity and [S].
Can plot the relationship between the velocity and substrate concentration
for the example of aspartate trans-carbamoylase. This doesnt produce a
hyperbolic curve —> doesn’t have a Michaelis-Menton relationship.
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 7 pages and 3 million more documents.

Already have an account? Log in

Get access

Grade+20% off
$8 USD/m$10 USD/m
Billed $96 USD annually
Grade+
Homework Help
Study Guides
Textbook Solutions
Class Notes
Textbook Notes
Booster Class
40 Verified Answers
Class+
$8 USD/m
Billed $96 USD annually
Class+
Homework Help
Study Guides
Textbook Solutions
Class Notes
Textbook Notes
Booster Class
30 Verified Answers

Related Documents

Related Questions