DHQ Flashcards
What does DHQ stand for? And what molecule does it act upon?
3-dehydroquinASE and dehydroquinATE
What kind of molecule is it? And how many types of it are there?
It is an enzyme, and 2 types.
What pathway is DHQ a part of?
The shikimate pathway, which is a biosynthetic pathway in plants and bacteria.
What does DHQ do in the pathway?
Removes water from dehydroquinate and puts first double bond into the 6-membered carbon ring.
What is the pathway useful for, biomedically speaking?
Herbicides in plants and the absence in animals means its an excellent target for microbials, knowing about it will be fabuloso for designing enzyme inhibitors
What do the two types of DHQ DO (both as an individual and differently from each other)
One of them catalyzes a cis-dehydration of dehydroquinate via a covalent imine intermediate. This is ONLY in the synthetic pathway. The other catalyzes a trans-dehydration via an enolate intermidate. This is in the biosynthesis pathway OR carbon and energy utilization.
What is the covalent imine intermediate?
Schiff base. This is a compound with a functional group that contains a C=N bond where the N is connected to an aryl or alkyl group, not a hydrogen.
How does the schiff base form? Draw the equation.
Enzyme-NH3+ + O=C-Substrate E-N=C-S + water + H+ The schiff base can be protonated on the Nitrogen to get rid of the free hydrogen ion.
How many subunits are in either type?
1 has dimers of identical subunits and 2 has dodecamers of identical subunits
What are the folds like in either type?
1 has 8-stranded parallel alpha/beta barrel. this is also found in other enzymes that perform similar reactions. 2 has 5-stranded parallel beta-sheet core, flanked by 4 alpha helices.
What evidence is there with the 2 types towards convergent evolution?
Well, both forms of DHQ have different structures, different sequences and different mechanisms but catalyze the overall same reaction.
Describe the folds of DHQ1 further
The open end of the barrel provides a large active site pocket. The other end is closed off by 2 short beta strands.
What is significant about the active site of DHQ1?
It is relatively small compared to the total volume of the enzyme.
How many amino acids are in contact with the enzyme in the active site of DHQ1? What do the other aa’s do?
Only a few, less than 10. Surrounding these is a larger set of AA involved in substrate recognition and binding.
What are the folds/loops doing when the substrate is in the active site of DHQ1?
THE LOOP IS CLOSED, on substrate binding arg213 forms a salt bridge w/substrate, locking it into position and the loop folds over the barrel, providing further interactions with the substrate. Lys170 forms the schiff base.
