km determination

Simon Easterbrook-Smith sbe at biochem.usyd.edu.au
Sat Dec 5 01:41:11 EST 1998


Dear Mike

It is probably most reliable to fit the M-M equation (v = Vm*S/(Km + S) to
the primary data (pairs of (v, S)) by non-linear regression analysis.

The problem with the various linear plots (Lineweaver-Burke et al.) is that
experimental errors can lead to distortion in the values of the parameter
estimates. Eg, in a Lineweaver-Burke plot large values of 1/v and 1/S have
the biggest effect on the parameter estimates but these data points
(corresponding to small values of v and S) are usually the least accurate.

Cheers

Simon 



|| Hello
|| I am currently working to determine the km's of our two different
|| enzymes of interest (isoforms), and am by no means a biochemist.  I am
|| wondering which is the best re-arrangement to determine the actual km. 
|| i have tried some initial data using Lineweaver-Burk plots, Hofstee
|| plats, Woolf plots and Scatchard plots.  Only the Scatchard and
|| Lineweaver-Burk plot agreed.
|| 
|| Is there a reference re which is the best plot depending on the data?
|| Should they all agree within a reasonable error?
|| 
|| Thanks in advance
|| 
|| Mike Allen
|| M.Sc. Student 
|| University of Waterloo
|| Ontario, Canada
|| m3allen at sciborg.uwaterloo.ca

-- 
_______________________________________________________________
Dr Simon B Easterbrook-Smith    Voice: (+) 612 9351 3905
Department of Biochemistry      FAX: (+) 612 9351 4726
University of Sydney            Email: sbe at biochem.usyd.edu.au
Sydney NSW 2006
AUSTRALIA
_______________________________________________________________
Under U.S. Code, Title 47, Chapter 5, Subchapter II, ß227, all
unsolicited commercial E-mail sent to my address from a U.S. account is
subject to a fee of $500.00 U.S. By E-mailing me you accept these terms.
cf. <http://www.law.cornell.edu/uscode/47/227.html>
_______________________________________________________________



More information about the Proteins mailing list