Chapter 8 Mechanisms and inhibitors Flashcards
What is Covalent catalysis?
The active site contains a reactive group, usually a nucleophile that is briefly covalently modified.
What is nucleophile?
its something that has a negative charge seeking positive charge
What is general acid-base catalysis
A molecule other than water donates or accepts a proton.
What is metal ion catalysis ?
Metal ions function in a number of ways including serving as an electrophilic catalyst.
What is Catalysis by approximation and orientation?
The enzyme brings two substrates together in an orientation that facilitates catalysis
What is an electrophile
A chemical that is electron deficient
How is the rate of an enzyme- catalyzed reaction affected by increasing temperature and what happens if the temperature is too high
It helps to enhance the rate but if it is too high it will also break the structure
Most enzymes have an __________ pH
optimal (So this means that at a certain pH the enzyme will perform better)
What is Competitive inhibition ?
The inhibitor is structurally similar to the substrate and can bind to the active site, preventing the actual substrate from binding
What is uncompetitive inhibition?
The inhibitor binds only to the enzyme-substrate complex. (it can only bind when the enzyme is bonded to the substrate) THIS ONE BINDS TO THE BINDING SITE
What is Noncompetitive inhibition?
The inhibitor binds either the enzyme or enzyme-substrate complex (this one binds regardless if the enzyme and substrate are bonded or not) THIS ONE BINDS TO THE ALLOSTERIC SITE ALSO KNOWN AS THE NON BINDING SITE
In competitive inhibition does the Vmax change ? Why or why not?
It is unchanged, because the inhibition can be overcome by a sufficiently high concentration of a substrate
What happens to the Km value in competitive inhibition?
IT increases in the presence of an inhibitor
What happens to the Vmax in uncompetitive inhibition?
-It is lower in the presence of inhibitor
- In this case you cant overcome the inhibition by the addition of excess substrate as it isn’t competing for the same spot.
What happens to the Km in uncompetitive inhibitions? is it higher or lower?
Lower
What does the competitive inhibition double reciprocal plot look like?
The lines will intersect on the y axis and the 1/Km will move closer to 0 and more steep if the inhibition is present
What does the uncompetitive inhibition double reciprocal plot look like?
the two lines are just parallel to each other
What does the noncompetitive double reciprocal plot look like?
The two lines intersect on the negative side of the x axis.
Irreversible inhibitors bind _______________ to enzymes
Very tightly
What do the group specific reagents react with?
R groups of specific amino acids. but only if the amino acid is exposed on the surface
How do affinity labels and substrate analogs inhibit the enzyme
They are structurally similar to the enzymes substrate but inhibit by covalently modifying an amino acid in the active site
How do the suicide inhibitors or mechanism based inhibitors inhibit the enzyme?
They bind to the enzyme as a substrate and as catalysis occurs the enzyme modifies the substrate converting it into ab irreversible inhibitor.
The enzyme basically kills itself in this one
What kind of enzyme is a chymotrypsin and what is it secreted by ?
it is a proteolytic enzyme and it is secreted by pancreas
What does a chymotrypsin enzyme do?
It hydrolyzes peptide bonds selectively on the carboxyl side of large hydrophobic amino acids.
What two steps does the Chymotrypsin proceed in >
- The rapid formation of an acyl-enzyme intermediate then a slower release of the acyl component to regenerate the free enzyme
HIstidine removes a __________from serine____,generating a ________________________
proton,195,Highly reactive alkoxide ion
_____________orients the histidine and renders it a better _____________
Aspartate, proton acceptor
Where is the oxyanion hole located?
In the region of the active site and it stabilizes the tetrahedral reaction intermediate
