20.01.2015 Views

Introduction to Enzyme and Coenzyme Chemistry - E-Library Home

Introduction to Enzyme and Coenzyme Chemistry - E-Library Home

Introduction to Enzyme and Coenzyme Chemistry - E-Library Home

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

198 Chapter 8<br />

aconitase<br />

citrate<br />

cis-aconitate<br />

− O 2 C<br />

−<br />

CO 2<br />

OH aconitase − O2 C<br />

−<br />

CO 2<br />

*H<br />

H<br />

−<br />

CO 2 H<br />

−<br />

CO 2<br />

*H<br />

H<br />

−<br />

CO 2 H<br />

−<br />

CO 2 − H<br />

O 2 C OH fumarase<br />

− O 2 C H<br />

− O 2 C<br />

− O2 C<br />

iso-citrate<br />

HO<br />

H<br />

O<br />

−<br />

CO 2<br />

H*<br />

CO 2<br />

−<br />

SCoA<br />

malate<br />

fumarate<br />

Figure 8.8 Reactions catalysed by aconitase <strong>and</strong> fumarase.<br />

Section 6.7, is single electron transport. What then is the role of an iron–sulphur<br />

cluster in a hydratase enzyme<br />

Determination of an X-ray crystal structure for mi<strong>to</strong>chondrial aconitase<br />

revealed that one of the iron a<strong>to</strong>ms in the cluster co-ordinates the hydroxyl<br />

group of isocitrate, as shown in Figure 8.9. This observation suggests that the<br />

Figure 8.9 Active site of aconitase (PDB Wle 1B0J). Bound isocitrate shown in black. Catalytic<br />

residue Ser-642 (on left) shown in red. 4Fe4S cluster: Fe a<strong>to</strong>ms shown in red; S a<strong>to</strong>ms shown in<br />

black; cysteine lig<strong>and</strong>s shown in black.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!