Carboxyl groups Flashcards
Tell me about ester hydrolysis and why they are important in metabolism?
- Triglycerides are converted to glycerol and fatty acids by lipases
- As with proteases, these reactions occur under remarkable mild conditions: 37˚c, near to neutral pH
- Lipases are extremely versatile and are often used in synthetic chemistry
Draw the different carboxyl functional groups?
Tell me about the characteristics of the carbonyl and the carboxyl group
Why is amide hydrolysis really important in the HIV life cycle?
- HIV protease chops up long polypeptide chains produced by translation into functional proteins
- HIV protease inhibitors are attractive targets for anti-HIV drugs
Compare amide hydrolysis in biological and chemical processes (acidic and basic)
What type of media can carboxyl substitution occur in?
basic or acidic
Draw the mechanism for carboxyl substitution in basic conditions ?
The general mechanism (addition-elimination): under basic conditions
Draw the general mechanism for carboxyl substitution under acidic conditions?
How many steps are there to this mechanism?
Whats the first part of the mechanism of carboxyl substitution under acidic conditions?
Whats the second part of the mechanism of carboxyl substitution under acidic conditions?
Is the mechanism really addition-elimination?
Draw the mechanism of acid-catalysed ester hydrolysis to carboxylic acids
Learn this mechanism pathway and how they link and what conditions are required
Why can’t esters be formed from carboxylic acids under basic conditions?
Drae the mechanism for basic amide hydrolysis
Whats Chymotrypsin and what family does it belong to?
It is a digestive enzyme and is a member of the serine protease family
In Chymotrypsin, what in its active site is critical to its catalytic activity?
What does it catalyse?
The serine residue in the active site is critical to its catalytic activity
It catalyses hydrolysis of proteins in the small intestine
Whats the catalytic triad and draw it?
- The three amino acids in the catalytic triad are Asp-102, His-57 and Ser-195
- They are central to the enzyme’s catalytic activity
Whats the catalytic mechanism?
In the catalytic mechanism, how is the intermediate stabilised?
- charge stabilised by an ‘oxyanion hole’
- Two backbone amide protons form a hydrogen bond
This shows the entire catalytic mechanism
What is substrate specificity determined by?
The properties and spatial arrangement of the amino acids forming the active site
How do small changes in the amino acid residues affect substrate specificity?
Small changes in the amino acid residues forming the active site will have a large effect on the substrate specificity of an enzyme.
Carboxyl groups can undergo substitution under what conditions?
Acidic or basic
but not all possible substitutions occur
What mechanism do all substituton reactions occur by?
via an addition-elimination mechanism with a tetrahedral intermediate
its crucial the intermediate is drawn in the mechanism
What do you need to consider with carboxyl substitution reactions?
- Is ‘Y’ a good enough nucleophile
- is the starting material sufficiently reactive
- which is the better leaving group ‘X’ or ‘Y’
- Is the product more or less reactive than the starting material
Are carboxyl substitution reactions reversible?
yes
Name 2 carboxyl substitution reactions which are important in nature
- ester hydrolysis in lipases
- amide hydrolysis in proteases
