Of the hundreds of cyp enzymes in nature only about 9 seem to be relevant to drug interactions. Many other enzymes are present in man such as the enzymes involved in the steroid pathway enzymes ie: 17 alpha hydroxylase, etc. There is an excellent searchable database at http://www.gentest.com/human_p450_database/index.html in which one can look up specific research documents regarding specific drug interactions. There is also the P450 Homepage maintained by Dr. David Nelson http://drnelson.utmem.edu/CytochromeP450.html which provides extensive links regarding the basic science of p450 systems.