I finally went to the Arabidopsis database and looked up the HOTHEAD gene mentioned in my previous post. Here is the database’s information on the gene. The detailed annotation of the gene, describes what is known or predicted about it:
- involved in cell-cell signaling (inferred from mutant phenotype)
- located in extracellular region (inferred from sequence or structural similarity)
- has mandelonitrile lyase activity (inferred from sequence or structural similarity)
- functions in FAD binding (inferred from sequence or structural similarity)
The predicted mandelonitrile lyase activity suggests that the gene may catylse the reaction of mandelonitrile = cyanide + benzaldehyde. Here are some details of the enzyme from Black Cherry.
FUNCTION: Involved in cyanogenis, the release of HCN from injured tissues. Catalyzes the stereospecific addition of HCN to a variety of aldehydes in vitro. It is a major seed constituent, and could have the additional role of a storage form for reduced nitrogen. CATALYTIC ACTIVITY: Mandelonitrile = cyanide + benzaldehyde. COFACTOR: FAD
None of this seems to help me get a clear picture right now. Anybody got any idea?