2cf5: Difference between revisions

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==Overview==

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.

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.

==About this Structure==

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[[Category: zinc]]

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@@ Line 4: / Line 4: @@
 ==Overview==
-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.
+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.
 ==About this Structure==
@@ Line 28: / Line 28: @@
 [[Category: zinc]]
-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Feb  3 10:34:33 2008''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:47:57 2008''