The red numbers in the chart represent enzymes that catalyze those steps; the blue arrows are transformations that we will not discuss explicitly.
Things to think about:
We'll take a look at a few of the enzymes of this path in enough detail to work out mechanisms for their catalysis.
To get us started, here are the first few steps and the enzymes that catalyze the steps:
Most organisms express multiple isozymes of DAHP synthase
|DAHP Synthetase (E. coli; 1kfl), Phe Bound||DAHP Synthetase (Yeast; 1of6), Tyrosine Bound|
Substantial similarity exists among the enzymes from different species
|Sequence Alignment of 1kfl and 1of6||Structure Alignment of 1kfl and 1of6|
The implication is that this is a very old biosynthetic pathway.
DQ synthetase also is a dimer in the biologically active state, requiring a Zn++ (purple) and an NAD+ in each unit to function.
It catalyzes a multi-step reaction sequence:
|Proposed Mechanism of Dehydroquinate Synthetase|
What was that about enzymes catalyzing single, specific reactions?
|Dehydroquinate Synthetase, with NAD+and Inhibitor||Catalytic Site of Dehydroquinate Synthetase|