Lecture notes
L11 Properties of Enzymes and Enzyme Kinetics
- Institution
- Kings College London (KCL)
First part of the two-part lecture on Enzymes by Prof Roberto Steiner
[Show more]
Seller
Follow
Content preview
L11 – Properties of Enzymes and Enzyme KineticsReview basics of enzymology: concept of catalysis, substrate specificity, effects of pH
and temperature on the rate of an enzyme catalysed reaction
Slide 5 – Definition/properties
• Enzymes are biological catalysts which speed up the rate of a reaction without altering
the final equilibrium between reactants and products
• Few enzymes are not proteins (eg. ribosomes)
• Extremely efficient
- Eg. The enzyme catalase catalyses the breakdown of its substrate hydrogen peroxide
to water at a rate 10^14 times faster than uncatalysed reaction at 30 degrees Celsius
Slide 6 – Effect of enzyme on activation energy of a reaction
• State of B is lower than A, and is therefore energetically favourable
• T: transition state, transition/activation energy you need to reach to go from A to B
• Lower peak, faster conversion of A to B
• Enzymes produce more suitable environment to allow A to go to B
• Transition state is not an intermediate or compound that you can chemically isolate
- Is a chemically unstable situation
Slide 7 – Enzyme catalysis
• Active site: physical location in enzyme where catalysis happens, where substrate binds
• Chemical reactions so that environment suitable for a particular reaction can be made
• Enzyme-substrate complex could be covalently or non covalently attached
• Product needs to have some affinity for active site, but has to have a lower affinity than
the substrate so the new substrate can come in and a new reaction cycle can happen
, • As reaction progresses, more product being formed, always some competition between
products in forming the enzyme-product complex
Slide 8 – Substrate specificity
• Enzymes usually catalyse only one type of reaction and will act on only a few related
molecules (‘group specificity’)
• A few enzymes are so specific they will only act on one substrate
• If a natural compound can exist in two stereoisomer forms, the enzyme concerned with
its metabolism in the cell will usually act only on one isomer
• Specificity is determined by presence of a groove or cleft of defined shape (active site)
into which only the substrate of correct shape and charge can fit
Slide 9-10 – Consequences of enzyme specificity
• Group of enzymes present together in one compartment of a cell
- Eg. Cytoplasm of muscle cells can create a complex and coordinated metabolic
pathway in which the initial substrate D-glucose is converted through a sequence of
specific enzyme catalysed reaction to product lactic acid
`
- B then acts as a substrate to the second reaction to make C
• Specificity of enzymes has led to a systematic classification scheme by IUB commission
on enzymes
• Enzymes divided into 6 main classes according to type of reaction they catalyse
- Class 1, oxidoreductases, contains enzymes catalase and alcohol dehydrogenase
- Six classes further divided into subgroups according to substrates or source
• Each enzyme identified by its own individual 4 digit number
- Eg. Catalase is E.C. 1.11.1.6
Slide 11-17 – Classification of enzymes
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller aurelianatasyaa. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
67096 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now