STRUCTURAL STUDY OF ARABIDOPSIS CAD5 (CINNAMYL ALCOHOL DEHYDROGENASE 5) ENZYME

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Lignins, lignans and isoflavonoids represent very important class of phenylpropanoids. They play important roles in plant defense, helping hosts discriminate between biological pathogens and symbiotic non-pathogens. More importantly, various final metabolic products of phenylpropanoid pathway have important pharmacological roles, especially in cancer prevention. Despite the importance of these compounds in plant biology and in human health, systematic studies on the enzymes involved have not been done. We have studied one of the most important enzymes involved in phenylpropanoid biosynthesis pathways. Cinnamyl alcohol Dehydrogenase 5 (CAD5) enzyme depicts a class of NADPH-dependent enzymes catalyzing the reduction of various phenylpropenyl aldehyde derivatives. Generically, this reaction makes several monolignols, with the latter mainly being precursors of lignans. We have already obtained the diffraction data of CAD5 crystal (P41212) with 2.5 ¿¿resolutions using a rotating anode (Rigaku, Raxis-IV). However, we couldn't perform the molecular replacement because there is no any similar protein solved. Therefore, MAD must be used. In addition to MAD data, the high resolution data and complex crystal (AtCAD5-cofactor/substrate/product) diffraction data are absolutely required for the studying of the exact mechanism of its unique stereospecific conversion of AtCAD5.