 |
PDBsum entry 2cf5
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Oxidoreductase
|
PDB id
|
|
|
|
2cf5
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Crystal structures and catalytic mechanism of the arabidopsis cinnamyl alcohol dehydrogenases atcad5 and atcad4.
|
|
|
Authors
|
|
B.Youn,
R.Camacho,
S.G.Moinuddin,
C.Lee,
L.B.Davin,
N.G.Lewis,
C.Kang.
|
|
|
Ref.
|
|
Org Biomol Chem, 2006,
4,
1687-1697.
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
The cinnamyl alcohol dehydrogenase (CAD) multigene family in planta encodes
proteins catalyzing the reductions of various phenylpropenyl aldehyde
derivatives in a substrate versatile manner, and whose metabolic products are
the precursors of structural lignins, health-related lignans, and various other
metabolites. In Arabidopsis thaliana, the two isoforms, AtCAD5 and AtCAD4, are
the catalytically most active being viewed as mainly involved in the formation
of guaiacyl/syringyl lignins. In this study, we determined the crystal
structures of AtCAD5 in the apo-form and as a binary complex with NADP+,
respectively, and modeled that of AtCAD4. Both AtCAD5 and AtCAD4 are dimers with
two zinc ions per subunit and belong to the Zn-dependent medium chain
dehydrogenase/reductase (MDR) superfamily, on the basis of their overall
2-domain structures and distribution of secondary structural elements. The
catalytic Zn2+ ions in both enzymes are tetrahedrally coordinated, but differ
from those in horse liver alcohol dehydrogenase since the carboxyl side-chain of
Glu70 is ligated to Zn2+ instead of water. Using AtCAD5, site-directed
mutagenesis of Glu70 to alanine resulted in loss of catalytic activity, thereby
indicating that perturbation of the Zn2+ coordination was sufficient to abolish
catalytic activity. The substrate-binding pockets of both AtCAD5 and AtCAD4 were
also examined, and found to be significantly different and smaller compared to
that of a putative aspen sinapyl alcohol dehydrogenase (SAD) and a putative
yeast CAD. While the physiological roles of the aspen SAD and the yeast CAD are
uncertain, they nevertheless have a high similarity in the overall 3D structures
to AtCAD5 and 4. With the bona fide CAD's from various species, nine out of the
twelve residues which constitute the proposed substrate-binding pocket were,
however, conserved. This is provisionally considered as indicative of a
characteristic fingerprint for the CAD family.
|
|
|
|
|
|
|
