Chemistry Reference
In-Depth Information
FIGURE 10.8
The phosphoglucomutase reaction proceeds via two phosphoryl transfer reactions.
(Adapted from
Allen & Dunaway-Mariano,
FIGURE 10.9
Active site of Methanococcus phosphoserine phosphatase with Mg
2
þ
and phosphoserine in the active site (a) and of human
phosphoserine phosphatase with Ca
2
þ
bound and the modelled substrate in the active site (b).
(From
Peeraer et al., 2004
.
Copyright 2004 with
permission from John Wiley and Sons, Inc.)
which ligates only one oxygen atom (
Figure 10.9
)
. This prevents the nucleophilic attack by one of the Asp 20 side-
chain oxygens on the phosphorus atom of the substrate, accounting for the inhibition (
Peeraer, Rabijns, Collet,
STABILISATION OF ENOLATE ANIONS
e
THE ENOLASE SUPERFAMILY
Yet another example of a family of Mg
2
þ
-dependent enzymes is the enolase superfamily which catalyse a series of
mechanistically diverse and different overall reactions. However, they all share a partial reaction in which an active
site base of the enzyme abstracts the
-proton of a carboxylate substrate to generate an enolate anion intermediate
which is stabilised by coordination to the essential Mg
2
þ
ion. This intermediate then is directed to different products
in the different active sites (
Figure 10.10
)
. The three 'founder' members of this family are the mandelate racemase
a
