BCEM 393 Lecture Notes - Lecture 9: Lactase, Chromogenic, Competitive Inhibition

70 views5 pages
Enzymes Part 3
ALMOST ALL BIOCHEMICAL REACTIONS FALL INTO A FEW TYPES
- Oxidation and reduction:
- For example the interconversion of an alcohol and an aldehyde/ketone
- Some steps in glycolysis and fermentation
- Movement of functional groups within or between molecules
- For example the transfer of phosphate groups from one oxygen to another
- In some steps of glycolysis
- Addition and/or removal of water
- For example, hydrolysis of an amide linkage to an amine linkage and a carboxyl group
- Bonding-breaking reactions
- For example a carbon-carbon bond breakage
- Found when original 6 carbon chain in broken down into 2, 3 carbon chains during
glycolysis
SIX MAJOR CLASSES OF ENZYMES
Class
Type of Reaction
Example
Oxidoreductases
Oxidation-reduction
Alcohol dehydrogenase (EC
1.1.1.1)
Transferases
Group transfer
Aspartate Aminotransferase (EC
2.6.1.1)
Hydrolases
Hydrolysis reactions
Chymotrypsin (EC 3.4.21.1)
Lyases
Addition or removal of groups to
form double bonds
Fumarase (EC 4.2.1.2)
Isomerases
Isomerization
Prolyl isomerase (EC 5.2.1.8)
Ligases
Ligation (joining) of two
substrates at the expense of ATP
hydrolysis
Carnosine synthetase
- Pneumonic to memorize 6 classes of enzymes: OFF TO HAWAII LIVE IN LUXURY (OFTH
LIL)
- An Enzyme Commission of the International Union of Biochemistry developed a classification
system for enzymes
- The identifier for each enzyme is EC followed by 4 numbers separated by decimals. The
first number indicates the major class
ENZYMES HAVE A FEW COMMON CATALYTIC STRATEGIES
- Ways for enzyme to decrease ∆G‡:
- Catalysis by approximation and orientation: The enzyme brings two substrates together in
an orientation that facilitates catalysis
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 5 pages and 3 million more documents.

Already have an account? Log in
- Covalent catalysis: The active site
contains a nucleophile (side chain) that
is briefly covalently modified
- General acid-base catalysis: A molecule
(eg. side chain) other than water
donates or accepts a proton
- Strain and distortion: Binding causes
stretching or compressing or twisting of
bonds to weaken them. Stretching a
bond weakens it, therefore less energy
is needed to completely break it. Thus,
activation energy (Ea) is lowered
- Metal ion catalysis: Metal ions function
in a number of ways including serving
as an electrophilic catalyst
TEMPERATURE AND PH
- Generally an increase in temperature
gives an increase in the rate of the
reaction
- For enzymes, this is true up to a certain
point at which the enzyme activity drops
off
- Organisms don’t increase temperature
- The shape of the activity vs. pH graph is
due to ionizable groups (side chains) in the
active site
- Question: Why does the rate decrease at high T? Because enzyme denatures at high
temperatures
- Question: Why does the rate increase as pH increases from 2 - 8? At the active site,
deprotonated COOH is needed
SUBSTRATES FOR CHYMOTRYPSIN
- Specificity: cleaves on the carboxyl-terminal side of large hydrophobic amino acid residues
- The 3D structure of chymotrypsin with an inhibitor bound shows a deep, relatively
hydrophobic pocket
- The pocket fits the substrate side chain of the residue of the substrate on the N-terminal side
of the peptide bond that will be cleaved
- This pocket determined the substrate specificity of chymotrypsin
Asp Lys
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 5 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Almost all biochemical reactions fall into a few types. For example the interconversion of an alcohol and an aldehyde/ketone. Movement of functional groups within or between molecules. For example the transfer of phosphate groups from one oxygen to another. For example, hydrolysis of an amide linkage to an amine linkage and a carboxyl group. Found when original 6 carbon chain in broken down into 2, 3 carbon chains during glycolysis. Addition or removal of groups to form double bonds. Ligation (joining) of two substrates at the expense of atp hydrolysis. Pneumonic to memorize 6 classes of enzymes: off to hawaii live in luxury (ofth. An enzyme commission of the international union of biochemistry developed a classification system for enzymes. The identifier for each enzyme is (cid:1688)ec(cid:1689) followed by 4 numbers separated by decimals. Catalysis by approximation and orientation: the enzyme brings two substrates together in an orientation that facilitates catalysis.

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