1yqx
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(New page: 200px<br /><applet load="1yqx" size="450" color="white" frame="true" align="right" spinBox="true" caption="1yqx, resolution 2.50Å" /> '''Sinapyl Alcohol Dehy...)
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Revision as of 02:23, 25 November 2007
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Sinapyl Alcohol Dehydrogenase at 2.5 Angstrom Resolution
Overview
We describe the three-dimensional structure of sinapyl alcohol, dehydrogenase (SAD) from Populus tremuloides (aspen), a member of the, NADP(H)-dependent dehydrogenase family that catalyzes the last reductive, step in the formation of monolignols. The active site topology revealed by, the crystal structure substantiates kinetic results indicating that SAD, maintains highest specificity for the substrate sinapaldehyde. We also, report substantial substrate inhibition kinetics for the SAD-catalyzed, reduction of hydroxycinnamaldehydes. Although SAD and classical cinnamyl, alcohol dehydrogenases (CADs) catalyze the same reaction and share some, sequence identity, the active site topology of SAD is strikingly different, from that predicted for classical CADs. Kinetic analyses of wild-type SAD, and several active site mutants demonstrate the complexity of defining, determinants of substrate specificity in these enzymes. These results, along with a phylogenetic analysis, support the inclusion of SAD in a, plant alcohol dehydrogenase subfamily that includes cinnamaldehyde and, benzaldehyde dehydrogenases. We used the SAD three-dimensional structure, to model several of these SAD-like enzymes, and although their active site, topologies largely mirror that of SAD, we describe a correlation between, substrate specificity and amino acid substitution patterns in their active, sites. The SAD structure thus provides a framework for understanding, substrate specificity in this family of enzymes and for engineering new, enzyme specificities.
About this Structure
1YQX is a Single protein structure of sequence from Populus tremuloides with ZN and NAP as ligands. Active as Cinnamyl-alcohol dehydrogenase, with EC number 1.1.1.195 Full crystallographic information is available from OCA.
Reference
Structural and kinetic basis for substrate selectivity in Populus tremuloides sinapyl alcohol dehydrogenase., Bomati EK, Noel JP, Plant Cell. 2005 May;17(5):1598-611. Epub 2005 Apr 13. PMID:15829607
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