Why the name?

In the last post I said the robot name of cytochromes P450 would be explained later. Now is the time! For that I will remount you back to the time whem CYPs were not even discovered.The presence of a weird pigment in liver microsomes, which presented a sharp absorvance peak at 450nm when ligated to CO,  were detected by Klingenberg in 1958. The nature of this peak remained unclear until Omura & Sato discovered in 1964 that it was due to the absorbance of an heme-protein. Not knowing which protein was that, they gave them the provisory name of Cytochromes P450 - because they absorbed light (CYtochromes) with a Peak (P) of absorbance at 450nm (450). This absorbance peak is now known as the Soret peak (http://en.wikipedia.org/wiki/Soret_peak).

                       Ryo Sato                              Tsuneo Omura

At that time, no one could imagine how diverse this family would be in terms of either forms, functions and widespread in biodiversity.
A year later, in 1965, a group leaded by Ronald Estabrook published in science the first described function for a P450 - it was the hydroxylation of the 17-hydroxyprogesterone to deoxycorticosterone.

more infos about that might be found at:
M. Klingenberg, Arch.Biochem.Biophys.75:376 (1958)
T. Omura, and R. Sato,J.Biol.Chem.239:2370 (1964)
D.Y.Cooper, S.Levin, S.Narasimhulu, O.Rosenthal and R.W.Estabrook, Science 147:400 (1965) 
http://www.issx.org/i4a/pages/index.cfm?pageid=3352