more P450 questions

Chuck Miller rellim at MAILHOST.TCS.TULANE.EDU
Wed Sep 11 11:07:07 EST 1996

Hi Tox Fans,

While we're on the subject........

I have recently had cause to start reading the P450 literature in a
critical manner. In many experiments the metabolism of a "specific"
substrate is used to assess the presence and activity of a particular P450
isoprotein. For instance, I have read papers stating that
ethoyresorufin-O-deethylase (EROD) activity is specifically measuring
CYP1A1 activity, while other investigators indicate CYP1A2 is also capable
of metabolizing this substrate. Is or isn't ethoxyresorufin a "specific"
substrate for CYP1A1? Is there a "specific" substrate that can discriminate
CYP1A1 from 1A2 activity?

Perhaps the problem is that a more careful or better defined use of the
word "specific" is needed, in that it implies that (as in this example
above) all P450s (and other enzymatic activities as well) except the
"specific one" have no activity against the substrate in question. This is
the definition I have in mind when someone tells me they are using a
"specific substrate" to assess a "specific" enzymatic activity. Is this a
resonable/logical definition for "specificity" ?

Best of results,


Dr. Charles A. Miller
Dept. Environmental Health Sciences, SL29
Room 374, Center for Bioenvironmental Research
Tulane Univ. School of Public Health and Tropical Medicine
1430 Tulane Ave.
New Orleans, LA 70112

More information about the Toxicol mailing list

Send comments to us at biosci-help [At] net.bio.net