The Shikimate Pathway - Biosynthesis of Aromatic Amino Acids

The shikimate pathway is the biosynthetic sequence employed by plants and bacteria such as E. coli to generate the aromatic amino acids: phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp):

outline of shikimate pathway

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:

Here are the first few steps and the enzymes that catalyze the steps:

line structures of first steps in the pathway

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

This must be 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

This page last modified 1:58 PM on Thursday April 10th, 2014.
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